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Chain Reaction

Chain Reaction 2

O nc e h o m e t o t h e f e w and heady,
the southwestern United States has experienced
a population explosion in recent years.
For example, Phoenix, Ariz., is home
to more than 1 million people, making
it the nation’s seventh largest city.
Surrounding cities, from Scottsdale to
Las Vegas, have also traded cactus blooms
for population booms. That trend may
spell the doom of desert tortoises.
Desert tortoises once roamed freely
throughout southwestern California, southern
Nevada, and western Arizona. Today they are in trouble.
The sad truth is that tortoises do not stand a chance against cars. Hundreds of
the animals are crushed every year by cars or off-road vehicles. Pet tortoises
released into the wild provide a new danger. These animals often take back
deadly diseases to the wild.
That story is the same throughout the world. Tortoise populations in
Africa, Asia, and South America shrink as human populations grow.
A group of researchers from The Phoenix Zoo and Arizona State University
is working to give tortoises a head start on their reproduction. A goal of their
Desert Tortoise Project is to help tortoise hatchlings grow up faster by chang-ing
their diets. This will let the animals lay more eggs during their lifetimes.
“For many tortoises, survival of the species is now a numbers game,”
explains ASU biologist Harvey Pough. “Each female must produce
at least two offspring who survive to produce just to keep the
population size stable.” That job is tougher than it sounds.
In the wild, desert tortoises do not reach sexual maturity—
when they can produce babies—until age 20. They then lay,
on average, three to seven eggs per year—which often get
eaten by coyotes, snakes, and Gila monsters. Very few
tortoise hatchlings survive their first year or two.
“A baby turtle is just an Oreo cookie to a predator,”
says Pough, a professor of Life Sciences at ASU West.
“The death rate of juveniles is about 95 percent
before age five.”
Pough and his team are testing a diet developed
by scientists at the National Zoo in Washington, D.C.
Those scientists found that desert tortoises grew
faster when they ate high-protein diets instead
of greens. They grew to full size in just five
years instead of the typical 20 years.
Speeding
by
Danielle Brooks
Slow and steady,
the fabled tortoise
eventually out-raced
the hare.Times have
changed. Today, the
desert tortoise is in
a race for its very life.
The competition—
smarter and much more
brutal—is human beings.
What is the difference between a turtle
and a tortoise? A tortoise is actually
one type of turtle that lives on land.
Unlike other turtles, tortoises only
go to water to drink or bathe.
The Desert Tortoise can live in places
where the ground temperature gets
above 140°F. It digs underground
burrows to escape the heat.
A desert tortoise spends at least
95 percent of its life in burrows.
C h a i n R e a c t i o n . 2 2
Tortoises
The National Zoo study did have a weakness. Many of the subject
tortoises were captured in the wild. As a result, no one knew their exact ages.
The ASU/Phoenix Zoo study fixes that problem by using only animals
whose age is known.
Researchers started in August 1995 with 24 hatchlings. They divided the
tortoises into two treatment groups. One group was fed a traditional zoo
salad diet. The second group got high-protein pellets as food.
Tortoises in the high-protein group were switched from zoo salad to
the experimental food. They had to be taught how to eat pellets. At first,
researchers ground the pellets into a powder and sprinkled it on the tor-toises’
greens. They were slowly weaned off the salad onto straight pellets.
The process took until March 1996.
By November 1999, tortoises in the protein group weighed about
twice as much as tortoises that ate salad. The average pellet-eater weighed
in at a hefty 800 grams, compared to 360 grams for the salad group.
The tortoise hatchlings in the
Desert Tortoise Project were placed
in quarantine for a month to ensure
a disease-free start. Tortoises from
different families were divided equally
between the study groups. This allowed
the researchers to factor in family
differences that might otherwise
affect the results. Like human families,
some tortoise families are naturally
bigger than others no matter what
they eat.
The sharp, serrated jaws of the
Desert Tortoise look a lot like a bread
knife. The jaws are perfect for shredding
tough grass and thick, pulpy cactus pads
and blossoms. The tortoise gets water
from its food and can store a month’s
supply in sacs under its shell.
3 http://chainreaction.asu.edu/
What do
desert tortoises
eat in the wild?
George Andrejko photo
“
”
This is the first time The Phoenix Zoo has participated in a collaborative,
scientifically based research project, according to Mike Demlong, the zoo’s
curator of ectotherms, or cold-blooded animals. “This study is helping the
zoo staff become better scientists,” Demlong says. “That is important, because
zoos aren’t just about fun and recreation anymore. We’re centers of conser-vation
and research. As such, we’re about building connections between
an increasingly urban population and the natural environment that
people are becoming more and more distant from.”
He says that the Desert Tortoise Project “is about inspiring
people to live in ways that promote the well-being of the nat-ural
world—even if it’s as basic as helping people understand
why they should try to avoid running over tortoises with
their all-terrain vehicles.”
Demlong says The Phoenix Zoo has dedicated special
summer and winter habitats to the Desert Tortoise Project, as
well as a total of about $300 per tortoise per year in food, facili-ties,
and veterinary care. “That’s a big investment for the zoo, given
that we receive no government funding. But it will be money well spent
if we can gain clear, conclusive data concerning the proper protein and
fiber diet ratios for head-starting healthy, high-quality tortoises,” he adds.
Demlong defines healthy as being free from all diseases—especially
respiratory disease and a common shell abnormality called “pyramiding.”
Pyramiding has been linked to other high-protein diets. As yet, it has not
affected The Phoenix Zoo tortoises.
Demlong defines high-quality tortoises as those able to forage, dig burrows,
avoid predators, and generally behave like tortoises in the wild. That is
important, he says, or else head-started tortoises will never be released.
ASU’s Pough agrees. “The real question is, even if the project’s ‘superju-veniles’
reach adult size within five years, will they be physiologically and
behaviorally mature? Will we have ‘young adults’ or ‘big babies’?” he asks.
This is the point where Ellen Smith enters the story. A scientist at ASU
West, Smith studies tortoises of the original National Zoo group at the Desert
Tortoise Conservation Center in Las Vegas. Those tortoises are now between
nine and 13 years old. Smith’s work focuses on social behavior and hormones.
Smith and her Las Vegas colleagues began by pairing up each superjuvie—
or head-started tortoise—with an opposite sex adult. Then they watched.
Tortoise “dating” behavior is a pretty strange sight. Normal adult tortoises
do a lot of nose-to-nose sniffing. Males “bob” their heads during courtship
and bite at the front legs of females. Females show their willingness to mate
by staying still. Otherwise, they just walk away.
The research group in Las Vegas watched to see if the superjuvies
showed these adult behaviors. They collected blood samples to compare
ASU scientist Harvey Pough says
tortoises play a unique role in the
desert. They are big and strong enough
to dig burrows in the tightly compacted
desert sand. Coyotes, snakes, lizards,
toads, insects, and mice all use
abandoned tortoise dens for their
own retreats. Tortoises dig burrows
throughout their 40 to 50 acre
ranges. Without them,
other creatures would
be at the mercy of the
desert’s extreme
temperature swings.
Scientist Smith glues a tiny plastic
identification tag to a hatchling.
If superjuvies could
reproduce at age five,
that would be four times
faster than in the wild.
That would be a clear
head start.
Ellen Smith
C h a i n R e a c t i o n . 2 4
John C. Phillips photos
“
”
hormone levels of the superjuvies to levels in adults. Adults that are
ready to reproduce have higher levels of sex hormones in their blood than
immature tortoises. The scientists also studied all eggs that were laid to find
out whether those eggs were fertile.
All the eggs from 1996 did hatch. Most female superjuvies did not lay any
eggs; the few eggs they did produce never hatched. Male superjuvies, on the
other hand, were able to successfully fertilize their adult partner’s eggs.
“Right now, I’d say superjuvie males appear mature while the females
seem unable to reproduce,” Smith says. “But not knowing the exact age
of the National Zoo tortoises makes interpretation difficult.”
Smith and the Las Vegas group will continue watching the female super-juvies
from the National Zoo to see when they begin to reproduce success-fully.
However, researchers expect data from the Phoenix study to answer
more questions because age, family relationships, and hibernation history
will all be known.
“Obviously, our ultimate hope is that superjuvies reach sexual maturity
at the age of five or six, and that the females continue producing
eggs until age 60 so they can help restore the population,”
Pough says. “The desert tortoise is a very important
species in the desert habitat.”
If we really can head-start
tortoises so that
they reach adult size in
five years or less, captive
breeding and release
programs for endangered
species may be possible.
We hope this method can
be used to head-start
other tortoise species
that are more endangered
than desert tortoises.
H a r v e y P o u g h
Desert tortoises lay eggs in May,
June, and July. An adult female might
lay four to eight eggs in a clutch.
She can produce two or three clutches
each season. Experiments have shown
that when tortoise eggs are incubated
at cooler temperatures (79-87°F),
they produce all male tortoises.
Warmer temperatures (88-91°F)
produce all females.
Male desert tortoises often fight
each other. The weaker male usually
runs away.
The desert tortoise stays cool inside
deep burrows that it digs in tightly
compacted desert gravel.
In order to get enough drinking water
in a dry climate, desert tortoises dig
basins in the soil to catch rainfall.
The Desert Tortoise Project is
a collaboration between ASU and
The Phoenix Zoo. For more information,
contact Harvey Pough, Ph.D.,
ASU West, 602.543.6048.
E-mail at Pough@asu.edu.
Or contact Mike Demlong at the
Phoenix Zoo, 602.914.4373. E-mail at
Mdemlong@phoenix-zoo.org
5 http://chainreaction.asu.edu/
Wh a t i s t h e b e s t w a y t o a t t r a c t g i r l s ?
A bright orange tail can help. It helps a lot if you are a chuckwalla
living among the rocks on South Mountain in Phoenix, Ariz.
Matthew Flowers is a graduate student at Arizona State
University. He studies chuckwallas. He wants to determine if
South Mountain chuckwallas are a brand new species of lizard.
Lots of chuckwallas live on South Mountain. In fact, within
the park’s boundaries, the concentration of chuckwallas is five
times higher than the normal density found in Southwestern
deserts. If you go chuckwalla hunting, you might find as many as 60
of the big lizards living in every hectare of territory.
Chuckwallas are big lizards. They grow to almost a foot in length and can
weigh as much as 12 ounces. They are the second largest of the 38 lizard species
found in Arizona. Gila monsters are the biggest. The average life expectancy
for a chuckwalla in the wild is 10 to 15 years, but some of the big lizards live
20 to 25 years.
“South Mountain Park contains a unique population of chuckwallas,”
Flowers says. “When I first arrived, the question was whether or not the
South Mountain population should be considered a new species of lizard.”
The Arizona Game and Fish Department currently protects the South
Mountain chuckwallas from collectors. The department supports Flowers’
research effort. The ASU scientist observes and collects live specimens.
Chuckwallas have very distinct color patterns. The colors provide an ideal
trait for studying the big lizards. Male chuckwallas often have different colored
tails. The typical tail color is white. Some have black tails. South Mountain
chuckwallas are unique. The entire tail on most males is bright orange.
Flowers converted his Tempe backyard into a chuckwalla enclosure.
He wants to know if female chuckwallas prefer one color tail to another.
To find out, he paints the tails of males. Then he tests specimens within
a population or between populations.
Brian Sullivan is an evolutionary biologist and ASU West professor.
He also is one of Flowers’ advisers. “Matthew's study of geographic variation
in chuckwalla mating behavior has generated widespread interest among evo-lutionary
biologists,” Sullivan says. “He is providing new understanding of
how environmental factors can shape differences in the behavior of males and
females of a species.”
Flowers makes behavioral observations on South Mountain during
all seasons, including the sweltering heat of an Arizona summer.
“We do focal animal observations,” Flowers explains. “We pick an animal,
watch it for half an hour, and then record its behavior. For example, I watch
the males fight. Then I mark down the color patterns of the winner.”
Chuckwallas are secretive reptiles. It takes time to gather enough data
ofTails
C h a i n R e a c t i o n . 2 6
Tales
of Tails
by
Dennis Durband
and Conrad J. Storad
South Mountain Park in Phoenix is
the largest municipal park in the world.
It covers 16,500 acres. The park features
unique geology and is home to many
different kinds of plants and animals.
Matt Flowers tracks chuckwallas in the
park with the aid of spotting scopes and
radio direction-finders.
A hectare is equal to 10,000 square
meters. How big is that? Two football
fields side by side would cover nearly
one hectare. If you went looking for
chuckwallas in other parts of Arizona,
you could expect to find about a dozen
chuckwallas per hectare.
about individual animals. Flowers says that the battles between male
chuckwallas can be an amazing spectacle.
“They lock jaws and roll around on the desert f loor,” he explains.
“Chuckwallas also make interesting social displays. Fighting is the ultimate part
of social interaction between the males. But they will try to solve issues before
fighting. They puff up their bodies and go through other physical displays,
including what appears to be a series of rapid pushups.”
Flowers logs his observations into a computer database. He uses the
computer to compare behavior, such as the number of pushups done among
individual chuckwallas over a certain time period.
Catching the big lizards can be painful. Flowers might spend anywhere
from five to 90 minutes trying to collect a single lizard. Chuckwallas retreat
from danger by wedging into rock crevices and inf lating their bodies. A well-entrenched
lizard can win the tug of war, forcing the frustrated scientist
to retreat, bloody fingers his only reward.
On South Mountain, female chuckwallas seem to prefer
males with orange tails to males with white tails.
“This suggests that they will only mate
with males from their own population,”
Flowers explains. “It also suggests that they
might be a different species. The fact that
South Mountain females prefer bright orange
tails over dull orange tails tells us more.”
Flowers says that orange tails may indicate the quality of a male chuck-walla’s
territory. The orange color is based on carotenoid pigments absorbed
from plants eaten by the individual lizard.
Chuckwallas also have good chemical senses. Tiny differences might
determine which male a female will select for mating.
“There probably are many factors that affect mate choice by female
chuckwallas,” Flowers says. “Male tail color is just one.”
There are 38 lizard species
found in Arizona.
Chuckwallas are the second
largest kind of lizards in Arizona.
The Gila Monster is number one.
What is a species?
There are millions of different living
things, or organisms, on the Earth.
Biologists have a system for naming
these organisms by grouping them into
categories. The categories allow people
to talk about the organisms and study
them in a logical way.
A species is one of the categories that
biologists use. A species is a group
of closely-related
organisms that
can breed together
and produce
offspring.
A Siamese cat
and a Russian blue
cat can breed and
have kittens.
Therefore, they
belong to the
same species. A Siamese cat and
a jaguar cannot breed—they are two
different species of cat.
It’s easy to see how a housecat and
a jaguar are different, but sometimes
the lines between species are blurry.
For example, sometimes people breed
different species of plants together
to produce hybrid crops. Even though
these plants are made to reproduce,
they still belong to different species.
The system isn’t perfect, but it has
been extremely useful for naming
and classifying life on Earth. So far,
scientists have found about 1.5 million
different species of animals, plants,
fungi, and microorganisms on our
planet.—Diane Boudreau
The Arizona Department of Game
and Fish support chuckwalla research
at ASU. For more information, visit
the ASU Research Magazine Web site—
http://researchmag.asu.edu
7 http://chainreaction.asu.edu
John C. Phillips photos
C h a i n R e a c t i o n . 2 8
AT HOME IN THE [Sonoran
C A T A L Y S T S Desert
make things happen.
They speed up reactions
and make some ingredients combine
that could not without them.
b y C o n r a d J . S t o r a d
Th e R e g a l H o r n e d L i z a r d
is active during the hot desert day.
It uses its tongue to slurp up ants.
George Andrejko photos
Space Shuttle astronauts in
orbit photographed the heart
of Sonoran Desert near Yuma, AZ.
B A J A C A L I F O R N I A
M E X I C O
A R I Z O N A
Phoenix
C
C
Hermosillo
T h e S o n o r a n D e s e r t i s
a n a r i d , r u g g e d p l a c e .
It also is a beautiful place filled with plants and animals.
Many of these animals and plants are unlike any other
creatures living on the Earth today.
The Sonoran Desert covers a large region of more
than 100,000 square miles. It spreads across north-western
Mexico, includes the Baja peninsula, and
covers the southeastern tip of California. To the north,
it stretches over a large section of southern Arizona.
The Sonoran Desert is a young desert. Scientists say that it has
existed in its current form for less than 10,000 years. It is very hot and dry
most of the time. Rain falls on a somewhat regular basis twice each year,
usually during the early summer and again during the winter.
Rain often falls all at once in violent storms streaked with lightning.
Sometimes rain does not fall at all for many months. Total rainfall
may amount to only seven to 10 inches in an entire year.
The Sonoran Desert is a living desert. It is not a sea of sand
and rocks. There are sand dunes, but only in a few areas. There
also are marshy, oasis-like areas called bosques, which form near
natural springs. Water in the desert means life. The Sonoran Desert
has water in the form of streams and washes from time to time.
But water does not often stay around for long.
9 http://chainreaction.asu.edu
Except for the tropical
rainforests of South America
or Africa, the Sonoran Desert
is home to more kinds of plants
and animals than any other
area of its size. These plants
come in many shapes and sizes.
So do the animals and insects.
T h e D e s e r t Wo o d R a t is also
called the Pack Rat. The rodent uses stones,
sharp sticks, and cactus spines to protect
the entrance to its burrow.
T h e A m e r i c a n
K e s t r e l is the
smallest falcon in
North America.
T h e D e s e r t
I g u a n a is active
at temperatures as hot
as 115 degrees. It can
grow more than a foot long.
P i p e v i n e Swa l l ow t a i l
male butterflies claim and defend
perches on ridges and hilltops
to keep watch for females.
The Saguaro C actus is the giant of the
Sonoran Desert, the only place it grows in the wild.
John Alcock photo
Tim Trumble photo
Desert plants are adapted to survive and f lourish
in hot, dry conditions. The roots are shallow nets or
deep straws that slurp up as much moisture as possible
following a rare rainstorm. Most have small waxy leaves
or sharp spines.
The Sonoran Desert’s animals and insects are just as tough.
Many desert mammals and reptiles are active only at dusk and
again at dawn. For this reason, it is rare for humans to meet
a javelina, jackrabbit, Gila Monster, or rattlesnake while
hiking during the day.
Bats, many snakes, most rodents, foxes, coyotes,
skunks, and other large desert mammals are
totally nocturnal. They sleep in a cool cave,
den, or burrow during the hot desert day
and hunt at night when the temperature
is cooler. Many desert birds are active during
the day. But they always perch in the shade.
Desert toads actually sleep most of the summer. They stay dormant deep
underground in moist soil until the summer rains fill the ponds. When they
emerge, they find mates and lay eggs quickly. The toads spend lots of time
eating and drinking to replenish their body reserves of food and water
for another long period of sleep.
Desert animals have developed many different ways
to find precious water. Some never drink water at all.
They get all the moisture they need from the plants
or insects they eat. The kangaroo rat and other
amazing desert rodents can actually make their own
water from the digestion of dry seeds. They will not
drink water, even if it is available by the bowlful.
C h a i n R e a c t i o n . 2 10
The Gila Monster is the largest and only venomous lizard found in
the United States. The big lizard’s teeth look like tiny grooved daggers.
Despite a fierce reputation, Gila Monsters actually are quite shy.
They spend most of the their time hiding in desert burrows
stolen from mice, squirrels, or other small rodents.
George Andrejko photos
Desert animals
have adapted
to live in hot,
dry conditions.
Can you explain
ways creatures
survive in
the desert?
The Mydid Fly is
active and mates
in the hottest part
of the summer.
The Antelope
Jackrabbit
is actually a
hare, not a rabbit
at all. Jackrabbits
rarely drink water.
They get all the
moisture they need
from the plants they eat.
Jackrabbits run in speedy
bursts up to 50 miles per hour.
The Jackrabbit’s foot-long ears help control
body temperature. During hot days, the long
ears stand straight up. Inside the ear’s thin
skin, a network of blood vessels gives off
heat, cooling the animal’s body.
On cold days, the ears lay back
close to the Jackrabbit’s body.
The Desert Cottontail
likes to munch on grass,
mesquite, and cactus.
Big-Eared Bats
hunt moths during the
night. Huge ears allow
them to fly and locate
food by sound, using
the echoes of their
ultrasonic squeaks.
Some bats can catch
up to 600 mosquito-sized
insects per hour.
K a n g a r o o R a t
11 http://chainreaction.asu.edu
The Roadrunner is the world’s fastest-running
flying bird. It prefers running to flying. About the
size of a skinny chicken, the speedy birds can take
12 steps in one second. Roadrunners have been
clocked zipping across the desert at speeds
up to 15 miles per hour.
The Collared Peccary is a piglike animal, but not actually a pig.
The name refers to the band of grayish-white fur around its neck. Heavy, bristly
hair covers a thin, muscular body. In Arizona, a collared peccary is known
as a Javelina. Javelinas have tough, leathery snouts, which allow the animals
to eat cactus and other spiny desert plants without injury to their mouths.
George Andrejko photos
The Bobcat snoozes on a warm
afternoon just like a housecat.
But don’t try to pet it!
The lone Coyote howling at the moon
is a symbol of the American West. In reality,
Coyotes are not solitary animals. They mate
for life and often hunt in packs, mostly
at night. Coyotes use at least 10 different
sounds to communicate, including barks,
yips, growls, and howls. Coyotes are
speedy runners. They cruise at 25 to
30 mph and can sprint at 40 mph for
short bursts, which is handy for catching
rodents, rabbits, and small deer.
The Ringtail cat is not really a cat.
Closely related to racoons, ringtails
are curious and active at night, some-times
stealing hikers’ food supplies.
Tiger Beetles are fast-moving
predators that catch and eat other
insects. They live in deserts and tropics
around the Earth. In India, people make
jewelry from the colorful wing cases.
Turkey Vultures
have a sinister reputa-tion
because they
eat stuff that would
make you hurl—
carcasses of dead
animals.
The Western Banded Gecko
feeds at night on spiders and insects.
C h a i n R e a c t i o n . 2 12
Th e Tarantul a Hawk is a big wasp.
The female uses a huge stinger to paralyze
tarantulas and other large spiders. Males
do not sting. The wasp lays a single egg
on the body of the paralyzed spider.
When the egg hatches, the maggot-like
larva burrows into the living spider and
begins to feed. The spider is helpless.
It actually may live for weeks or
months as the wasp larva devours
him from the inside out.
ASU biologist John Alcock
studies the big wasps. He marks
harmless males with paint. Alcock has
tracked a single wasp for up to 40 days in the field.
More than 35 different kinds of scorpions live in Arizona.
But only one species – the Bark Scorpion — has venom
potentially strong enough to kill a person. Don’t give
yourself nightmares. The last documented case in Arizona
of a person dying from a scorpion sting occurred in 1948.
A spider’s front jaws are called
chelicera. The chelicera
include the fangs.
The Giant Desert H a i ry Scorpion
is the largest scorpion living in the United States.
It can grow up to 6 inches long.
Desert scorpions never venture far from
the burrows they dig in loose, sandy soil.
“Chela” is the name for the scorpion’s
pincer-like appendages. Scorpions walk
with their chela extended.
Tarantulas and scorpions are arachnids.
Arachnids belong to the largest group of animals
now living on the Earth. Arthropoda is the scientific
name for this group, which scientists call a phylum.
Creatures in this group are called arthropods. The phylum
Arthropoda includes arachnids such as spiders, scorpions,
ticks, and mites. It also includes centipedes, millipedes,
crustaceans such as crabs, shrimp, and lobsters, and millions
of kinds of insects. Fossil evidence indicates that ancestors
to modern scorpions might have been swimming in
ancient oceans as long as 450 million years ago.
Paula Jansen photos
John Alcock photo
13 http://chainreaction.asu.edu
&stingers
fangs Tarantulas and scorpions are cousins. They may look like monsters from outer space,
but they actually are very shy creatures. They want nothing to do with humans. There are no
tarantulas in Arizona or the United States that are considered dangerous to humans. You are in
more danger from fainting and hitting your head than you are from the bite of a desert tarantula.
Mexic an Redknee Tarantul a
Tarantulas catch insects and tear them
into pieces. The pieces are rolled into
a large “food ball.” The spider then
gushes digestive fluids onto the ball
and slurps in the gooey bug stew.
Hard pieces are left behind.
In the Sonoran Desert, tarantulas spend
most of their lives living inside small
burrows that they dig in the desert soil.
They leave the burrow at night to hunt
for crickets, grasshoppers, beetles,
cockroaches, and other small creatures.
Better to be a girl? Most male tarantulas
only live between six and 18 months.
Female tarantulas can live for 20 or
30 years, depending on the species.
C h a i n R e a c t i o n . 2 14
RTraackintg tle
Camping g e a r a n d r e searc h eq u i p m e n t cram the back
of Emily Taylor’s truck. Beside her sits a plastic bucket secured with
a screw-top lid. Two female Western diamondback rattlesnakes
are snoozing inside.
Taylor is crossing reservation lands between Phoenix and Tucson to return
the snakes to the wild. She is headed toward the research site she and her
advisor, veterinarian Dale DeNardo, have staked out on land near the Tortalita
Mountains. Earlier that week in their ASU laboratory, the two scientists surgi-cally
implanted a radio transmitter under each animal’s ribs. Each transmitter
broadcasts a beeping signal at its own unique frequency. Using a receiver,
Taylor and DeNardo can locate the snakes in the field by following the signals.
This technology is called radio telemetry. The technology really helps
scientists who study reptiles. Just imagine trying to find the same snake twice.
In the past, researchers marked rattlesnakes by painting or injecting their
rattles with paint in coded patterns. That helped them to recognize a snake
if and when they were lucky enough to find it again.
Laboratory conditions can cause animals to behave differently than they
would in the wild. To study patterns in animal behavior, scientists must watch
the animals over time in their natural environments.Unfortunately, this makes
it very hard to keep track of them. Radio telemetry lets scientists find an animal
even when it moves to a new location.
The road into the research site soon turns into a heaving trail. Taylor shifts
into four-wheel drive. Her truck bucks its way to a wide space in the track.
She parks beneath heavy rust-colored buttes that rear up against a hazy sky.
It is just before dusk, the moment when shadows define the curves of desert
rock that look two-dimensional in midday sun.Armed with her radio receiver,
Taylor crunches through gravel to search for some of the more than 20 reptiles
she is following.
She and DeNardo are studying snake biology on several levels. First, they
want to document the basic ecology and habits of the western diamondback.
Scientists still have important questions to answer about the snake.Forexample,
no one knows much about its denning behavior.Why do animals that hunt and
sleep alone hibernate in groups?Why do researchers findmainly large,mature
males in those dens? Why do young and small males seem not to be included?
Emily Taylor’s
area of research
is called behavioral
neuroendocrinology.
She studies how
hormones trigger
an animal’s brain
to command certain
actions, such as
breeding.
by Kristine S. Wilcox
Herpetology:
The study of reptiles
and amphibians
In mammals, the fatter the animal, the
more leptin is found in the bloodstream.
In fact, leptin comes from fat cells.
The hormone tells the brain how much
fat the body has stored. When it detects
large amounts of leptin, the brain
signals the body to decrease feeding
and increase production of heat, which
uses energy. When leptin is low,
the brain tells the body to increase
feeding and decrease heat production
to conserve energy.
15 http://chainreaction.asu.edu/
ers Second, the ASU scientists want
to compare individual diamondbacks
within a particular area. Other
researchers compare individuals
of other rattlesnake species. Scientists will
eventually be able to put their knowledge together
and compare the various species from an evolutionary perspective.
Third, they want to learn how snakes allocate energy to reproduction.
Taylor’s main research interest lies in this area. She wants to know how
hormones in the female diamondback trigger breeding and the energy
use that fuels it. She says that the key is fat.
“In any female animal, fat is crucial to reproduction,” Taylor says.
“If an animal is undernourished due to drought or other stressful conditions,
she won’t attempt to breed that season. If she did, breeding would divert
fat from supporting her life systems to manufacturing yolk for her eggs.”
Taylor wants to know exactly what happens in a female snake’s brain
that tells her she has enough fat to breed. Taylor and DeNardo suspect that
a hormone called leptin is involved. Scientists know that leptin helps
to regulate eating and reproduction in mammals. They know that reptiles
produce leptin. But they don’t know what function the hormone plays
in the reptile body.
Researchers have learned that leptin allows female mammals tomenstruate
and ovulate. Taylor wants to know if it also signal a female mammal to breed.
If so, does this happen in rattlesnakes as well as mammals?
To answer these questions, Taylor and DeNardo spend four to five days
per week at the field site tracking their tagged reptiles.The scientists surrender
to the rhythms of the desert and live like lizards. They stalk prey in the cool
mornings and evenings. They snooze and swim at a nearby RV park during
the midday heat.
Typically, either Taylor or DeNardo arrives at the site in late afternoon.
He or she will track the animals until about 10 p.m. Then they sleep under
the stars and rise to track again with the sunrise. The goal is to follow the
animals through a season’s birthings, which occur in August. By November,
the rattlesnakes will retreat to dens for the winter.
The ASU scientists weigh the snake each time they recapture an animal.
By comparing a female’s pre- and post-birthing weights, they can figure out
how much fat and protein snakes invest in their babies. Two knots snarl
the research question. Taken alone, a female’s weight change does not show
“ how much energy she has put into reproduction. Exercise or diet rather than
pregnancy might have caused the change. Also, the researchers need to know
how much of the weight change is because of protein and how much is fat.
To find out, Taylor and DeNardo are using a technique commonly used
to measure body fat on humans. The method involves sending an electrical
signal through the body. The signal travels at different speeds through fat
and protein. After some number crunching, this information lets researchers
estimate the animal’s body fat percentage. Armed with this measurement,
the scientists will then factor in the animal’s movements (exercise) and the
food supply (her diet). They can then estimate how much body fat energy
the female has used to make babies.
Every three to four weeks, the researchers draw blood from the reptiles
to measure hormone levels. Taylor has one priority on this particular field visit.
She wants a blood sample from a female diamondback that she has been try-ing
to catch above ground for three weeks. With reptiles, the question
is always, is the animal up on the surface? Or is it down in a burrow? Radio
equipment may pinpoint an animal’s location. But if a rattlesnake is curled up
in a burrow, Taylor cannot just ring the bell and ask the snake to come out.
With her blonde ponytail swinging, a coiled serpent tattoo on her ankle,
Taylor strides along the soft-gravel washes that curve through the desert like
highways. Taylor holds the simple tools that protect her. In one hand is a pair
of plastic snake-handling tongs. In the other, a clear plastic tube, cloudy with
scratches, that is about as long as her forearm. A student intern lugs the plastic
bucket holding the snakes Taylor is returning.
Taylor always listens for the hissing rattle of a snake. She listens close in
washes where the scales of the diamondback blend into the gravel, and around
patches of prickly pear cactus, in which the vipers often seek burrows.
“The real danger out here is getting careless and stepping on a snake,”
she says. Suddenly, Taylor spots a snake. Stretching ahead of her in the wash
is a male diamondback, about three-and-a-half feet long. “Oh look at you,
bad boy,” Taylor says. “You are a beautiful boy.” She rushes toward the snake,
which tries to escape into the brush.
Rattlesnakes are slow. They cannot crawl more than about three miles per
hour. Taylor clamps her tongs around the snake’s body, holding it at full arm’s
length. The animal begins the defensive displays that it uses against predators.
Its muscled body thrashes. Its rattles clash furiously against one another.
Its pink cave of a mouth gapes and hisses. Foul smells seep from its cloaca.
With her right hand controlling the tongs, Taylor uses her left to bring the
tube toward the rattler’s head. Again and again the snake strikes the plastic
C h a i n R e a c t i o n . 2 16
Studying reptiles gives you a great evolutionary
Occupational
Hazard
“The term ‘usually’ should never
be applied to venomous reptiles,”
cautions rattlesnake researcher
Emily Taylor.
For example, snakes being coaxed
into a tube usually strike at the tube,
not the person holding it. But that
didn’t matter much when “Lucifer
the Jumping Snake” decided one day
to sink its fangs into Taylor’s hand
instead.
“He jerked his head out,” Taylor says,
“and sprang up to bite my hand.
Usually the snake won’t behave this
way. He’ll strike the tube, because it’s
the closest thing to his face.”
Nature is never entirely predictable.
Forgetting that in Lucifer’s case,
says Taylor, was her mistake.
Worldwide, every year, several hundred
thousand people are bitten by venomous
snakes. Of those, some 20,000 die.
Most deaths occur in Third World
countries with poor access to medical
treatment. Properly treated, snakebites
in developed countries cause death
in less than 1 percent of victims.
In the United States, most bites occur
when untrained people handle snakes
in the wild. Some victims die simply
because they refuse medical care.
Of nine snakebite deaths in Arizona in
recent years, three happened to victims
who refused treatment.
Almost all the old folk remedies for
snakebite are useless or dangerous,
according to experts. You should never
cut into a bite wound to suck out venom,
or apply a tourniquet unless a doctor
says to do so. >>
” with sharp snaps. The scientist is trying to lure the diamondback into the tube.
Finally it goes in, shooting about half the length of its body into the plastic
pipe. Now Taylor grips the tube and the tail end of the snake in one hand.
The tail hangs free, while the dangerous head is trapped in the tube.
“The snake could turn around in the tube, shoot back out and get your
hand,” Taylor explains. “Never take your eyes off a tubed snake.” She learned
this lesson the hard way (see sidebar).
Scientists don’t know why snakes enter the tube. “It may remind them
of heading into a burrow to escape a predator,” says Taylor. “Maybe it’s an
instinctive defensive move. They’ll fight going in, but sooner or later they all
go in.” Besides, she says, “They’re not super bright. The tube is in the forward
direction, and eventually they just go forward.”
Taylor pulls a syringe from her pack and bites the cap off the needle.
The intern takes the tube, and Taylor works the needle into the snake’s smooth
skin, seeking a vein near the rattles. She finds it and blood fills the syringe.
With another syringe she shoots acrylic paint into its rattles to identify it
with a three-color code.
Rattlesnakes are cold-blooded creatures. A snake feels cool to the touch.
Its body is very muscular. The underside feels slick as the hull of a fiberglass
boat. On top, you can click a thumbnail down the edges of the scales.
Taylor dumps the diamondback tail-first into a bag, then into the bucket
with the others. Later, she will weigh it, record its location, and return it
to the discovery site. This is the only new snake Taylor finds on this trip,
but she does find the female that has been eluding her. Taylor is thrilled to
draw the snake’s blood, saying how pleased her advisor will be that she got it.
Through the night and again the next morning at daybreak, Taylor doggedly
tracks each animal she must account for. She never loses her way, although she
crosses several square miles. The heat and exercise do not seem to tire her.
Her passion for her work keeps her energized.
Lots of peoplemight ask why Taylor is interested enough in snake hormones
to wrestle with rattlers. She points out that, for human beings, all biology
leads to self-understanding.
“Studying reptiles gives you a great evolutionary perspective,” she says.
“Remember, reptiles gave rise to mammals. Besides,” she adds, “some of the
biggest discoveries in science occur during basic research,kind of by accident.”
“I’m not saying that I expect to find the cure for AIDS by studying snake
hormones,” Taylor admits. But she does expect to add facts to the scientific
understanding of snakes.
17 http://chainreaction.asu.edu/
perspective,” Emily Taylor says.
“Remember, reptiles gave rise to mammals.
Poison control experts agree that the
best first aid for snakebite is to keep the
victim calm and warm to prevent shock,
and to seek medical help immediately.
In Taylor’s case, she received standard
treatment with antivenin—a serum that
neutralizes the poison.
She feared antivenin more than snake
venom. Antivenin is made from horse
serum. Horse serum causes intense
allergic reactions in 98 percent of all
patients. Symptoms can include rashes,
fever, and joint stiffness. Doctors treat
the reaction with steroids and antihista-mines.
Taylor did suffer a reaction after
her treatment with the antivenin.
But she responded quickly to treatment
and was handling snakes again within
a week.
“I have a renewed sense of care and
appreciation for these snakes, now,”
the ASU scientist says. She intends
to keep a “much larger buffer zone”
between herself and her snakes
in the future. Kristine S. Wilcox
Snake surgery Emily Taylor operates
on a captured rattler to implant a radio transmitter.
I n t h e S o n o r a n D e s e rt , some tigers hunt
during the day. Others hunt only at night. All desert tigers
use excellent eyesight to locate their prey, and then use
amazing speed to run it down.
The hunted creature has little chance. Once caught, the tiger crushes
it with huge, sickle-like jaws, and then tears it into pieces. The tiger pours
powerful digestive juices from its mouth onto the bits and pieces. Once
the pile of pieces is melted into a nice, gooey mush, the tiger rolls it all
into a large meatball. Then it is time to chow down.
Tigers in the Arizona desert? No way, you say. Believe it.
But these tigers are not giant cats. They are beetles. Their food
of choice includes ants and termites and small insects of all kinds.
David Pearson studies these fierce desert hunters. Pearson is an
ecologist and conservation biologist at Arizona State University. Tiger beetles,
he says, are fascinating, colorful predators. The insects are extremely popular
among amateur entomologists. Often brightly colored in greens, maroons,
or metallics, tiger beetles are the beauty queens of the insect world.
Pearson has circled the globe for his research,
studying beetles in South America, India, Africa,
Europe, Indonesia, and the United States.
Arizona is famous for its variety of tiger beetles.
The state is home to 36 different species, which live every-where
from the Chiricahua Mountains in southern Arizona
to the North Rim of the Grand Canyon. The beetles are
especially fond of the Sulphur Springs Valley in southeastern
Arizona, where 18 different species live. That is one of the
highest concentrations of species in all of North America.
Tiger beetles in Arizona grow from 10 to 25 millimeters
long. Most are brown or green with stripes. Most are active during the day.
Some are large and black and active only at night. The best time of year
to see tiger beetles depends on where you look.
The insects are active from February to April in Sedona and along
the Mogollon Rim near Payson. In July, they can be found in the White
Mountains. In southern Arizona, tiger beetles are active at the start of the
summer monsoons.
Pearson studies tiger beetles because they lend themselves easily to
conservation studies. These insects make good bioindicators. A bioindicator
is a species that serves as a representative sample of its ecosystem.
Bioindicators allow scientists to make predictions about the ecosystem
without studying every species in it. Tiger beetles are highly sensitive
C h a i n R e a c t i o n . 2 18
Teigrreirbsle
b y D i a n e B o u d r e au
O F T H E D E S E R T
Cicindela oregona maricopa—
Kim Wismann Photo
Cincindela lemniscata—Kim Wismann Photo
About 2,300 species of tiger beetles
(family Cicindelidae) exist worldwide.
They live everywhere there is land,
with the exception of Antarctica,
Tasmania, and some of the most
remote oceanic islands.
Tiger beetles primarily live in tropical
areas. The United States is home to
120 different species.
All the beetles shown here were found
in Arizona.
to changes in their environment, an important characteristic.
“In conservation biology we’re always short of money, time,
and personnel. We need to make policy decisions. Bioindicators
provide a quick way to find answers with a high degree of accuracy,”
explains Pearson.
“Bioindicators are kind of like the canaries in a coal mine,”
explains Pearson. “The canaries were very sensitive to methane gas—
much more so than human beings. These big burly miners would
carry down these little cages with canaries.
If the canary all of a sudden keeled over, people
ran quickly out of the mine, because they didn’t
have a lot of time, but at least they had some
kind of warning as an indicator of the danger.”
Tiger beetles vary in size.
The smallest lives in Borneo and
measures 6 millimeters, about the
length of a housefly. The largest lives
in southern Africa. It measures up to
45 millimeters, about the width
of a tea bag.
Tiger beetles come in many colors.
Some are plain black, but others are
stunningly decorated in metallic green,
brown, maroon, or purple, often with
stripes or spots. All tiger beetles have
long, thin mandibles shaped like
sickles, which help them capture prey.
Tiger beetle larvae use their mandibles
to dig tunnels in the ground, where
they wait for small insects to pass
close enough for capture. The larvae
stay in their tunnels from one to three
years before emerging as adult beetles.
An Australian tiger beetle takes the
prize as the fastest runner of all the
arthropods, a group that includes all
insects, crustaceans, and arachnids.
This beetle can move at 9 kilometers
per hour (5.6 miles per hour), or 170
body lengths per second. If it were the
size of a racehorse, the beetle would
be running about 120 miles per hour.
Consider this: a human traveling 170
body lengths per second would have
to run about 338 miles per hour, or 544
kilometers per hour! The tiger beetle
is a tough bug to catch, or to outrun.
19 http://chainreaction.asu.edu/
“You can’t just choose bioindicator
species because you like them,
because they’re soft and furry.”
Cincindela pulchra—Kim Wismann photo
Paula Jansen photo
Eleodes or darkling
beetle that has been dis-turbed
and is in the warning
position, with rear abdomen
6
Bugs It could be Halloween at Brimhall Junior High School in Mesa.
Kids are emptying bags. They count and compare their loot like hungry
trick-or-treaters. However, they are not finding candy bars and lollypops
in the bags. More like a bunch of ants and a handful of beetles.
Perhaps there are a couple of crickets
in the mix. Once in a while there
is a real prize—a giant centipede
or even a scorpion!
These treats are no trick.
The bags of bugs are actually part
of David Boomgaard’s science class.
They are also part of something bigger.
Brimhall is just one of several schools
taking part in the Central Arizona–
Phoenix Long–Term Ecological Research
project—CAP LTER for short. Scientists
from Arizona State University’s Center for Environmental
Studies and the CAP LTER project are studying how city life
in the desert affects our air, water, plants, and animals—including bugs.
The bug work is known officially as the Ground Arthropod Study.
Arthropods include insects, arachnids (such as spiders and scorpions),
crustaceans (lobsters, shrimp, and crabs), and myriapods (centipedes and
millipedes). Ground arthropods are creatures that
crawl on the ground. They do not f ly or swim.
Most people try to squash bugs. They shouldn’t.
Insects are actually a very important part of the
ecosystem, says Nancy McIntyre, the ASU scientist
in charge of the arthropod study. “There are more
different types of bugs than any other kind of living
organism on the planet,” she says. “They’re the most
diverse group of critters in the world.”
Arthropods also play important roles in
the environment. They are critical links in
the food chain, both as predators and prey.
They also aerate soil, pollinate crops,
and do a variety of other essential jobs.
There are lots of LTER sites all over
the United States. Scientists have
been doing long-term research on different habi-tats
for more than 20 years. But the Phoenix LTER
site is new. It is one of only two sites located in
cities. The other city site is Baltimore, Maryland.
C h a i n R e a c t i o n . 2 20
What is an Insect?
Insects have three major body sections:
Head, thorax, and abdomen
The head contains the one set of large
compound eyes, mouthparts, and one
pair of antennae
Six walking legs and one
or two pair of wings attach
at the thorax
Going Buggin’
by Diane Boudreau
darkling beetle
assumes the warning position.
This common desert beetle
protects itself by firing
a chemical that smells
and tastes bad. Have
you seen these beetles
in your neighborhood?
The hover fly looks and acts like a bee.
It’s a trick to make a harmless animal appear
uninviting to predators.
Conrad Storad photo
John Alcock photos
“Bugs in cities have been under-appreciated until very recently,”
McIntyre says. Now, CAP LTER researchers are finding that urban areas
are home to more than just roaches and ants. “It’s pretty amazing that a city
as large and as sprawling as Phoenix has such a diverse bunch of bugs.
So far, we’ve captured nearly 90 types of arthropods here,” says McIntyre.
CAP LTER scientists collect bugs from 24 sites. The sites are divided
into six different types of habitats. Phoenix-area schools that participate
in the bug study add their own special habitat: schoolyards.
“We wouldn’t normally have access to a whole bunch of schools,”
McIntyre says. “We wouldn’t have the people power, we wouldn’t have
the time, and we wouldn’t have the money.” So teachers and students
contribute a lot to the project. Twenty schools are involved in the project
at this point, almost doubling the number of sites being studied.
CAP LTER’s Ecology Explorers program works with local schools to teach
kids about ecology and get them involved in the experiments. Monica Elser
is an education liaison for Ecology Explorers. She says that Arizona students
basically do the same research as the CAP LTER scientists.
The first step is to set traps to catch the bugs. Students bury plastic
cups so that the tops are level with the ground. Bugs fall into the cups,
but they can’t climb out because the sides are too slippery.
The Grey Hairstreak
is a highly territorial butterfly.
The males defend perching sites on hilltops.
The Buprestid Beetle
is a wood-boring insect.
Some types specialize
in feeding on the pungent creosote bush.
Great Purple Hairstreak adults
sip nectar from mesquite and mint flowers.
The caterpillars feed only on the
leaves of mistletoe.
21 http://chainreaction.asu.edu/
CAP LTER scientists collect bugs from 24 sites.
The sites are divided into six different types of habitats:
+homes with lawns
. homes with desert landscaping
P industrial areas
R farmland
e desert parks within the city (like Papago Park)
b desert parks on the edge of the city (like Estrella Mountain Park).
Phoenix-area schools that participate in the bug study
add another category to the mix:
c schoolyards
Black Widow
venom, drop for drop,
is 15 times more powerful
than that of a rattlesnake.
But a rattlesnake is
much more dangerous
because it produces
much more venom.
Marty Cordano photo
John Alcock photos
8
What is an Arachnid?
Arachnids have only
two major body sections:
Cephalothorax and abdomen.
Head and thorax are fused to form
the Cephalothorax; a thin waist
connects the two body parts.
Eight walking legs
Many eyes, as many as 6 or 8
No antennae
No wings
After collecting the bugs, the kids immediately put them into labeled
Ziploc bags. Then they freeze the bags, bugs and all.
Elser says the freezing is very important. It is difficult to study bugs
closely enough to identify them when they are moving. Freezing is also
an important safety measure, because students occasionally catch scorpions
and other venomous arthropods.
Students identify the creatures using a key that CAP LTER provides.
They catalogue the bugs by order, such as Hemiptera (true bugs) or Coleoptera
(beetles). The students count how many of each type they find, and then
send the data to the CAP LTER Web site on the Internet.
“The kids become experts at identifying the insects.
They don’t need the keys after a while,” Boomgaard says.
“I couldn’t even identify them before I joined
the program, and I’m a biology teacher!
“We mostly find beetles and ants. Every
once in a while we get some surprises,” he adds.
“We’ve caught some bees, which are a surprise
because normally they just f ly away. We’ve
caught crickets and cockroaches. We even
get the odd gecko or two in the cups.”
Elser says that most students find lots of
beetles, grasshoppers, crickets, roaches, true
bugs, and ants. Once in a while, students will
find a scorpion or giant desert centipede as well.
McIntyre hopes the program will teach
kids not to just kill bugs automatically. “A lot of
people are really afraid of arthropods,” she says.
“They think they’re going to bite or sting, but
most of them don’t. I know from personal expe-rience
that when people are afraid of things they
tend to kill them. A great example is dragonflies.
People are scared to death of dragonflies.
But dragonflies are completely harmless.”
Not only are most bugs harmless, many of them are pretty, too. “There
are a lot of beautiful patterns that you can only see up close,” Elser says.
What do Boomgaard’s Mesa junior high students think of the project?
“I remember a kid saying last year, ‘This is really cool. We don’t just
learn about science, we go out and actually do it,’” Boomgaard says.
The CAP LTER scientists are just as happy about the project.
“All the students are helping us out,” says McIntyre. “They cover
20 sites that we wouldn’t otherwise be able to study.”
Bugged by Bugs
It flie s. It crawls.
It is small and funky-looking.
It’s a bug,
right? Well, not
exactly.
Most people use
the word “bug”
to refer to all
insects. But tech-nically,
not every
insect is a bug.
True bugs, as they
are called, do not
include such buglike
creatures as ants, bee-tles,
or flies.
True bugs look
a lot like beetles, because they
have hard shells and wings. The dif-ference
is in their mouths.
Beetles have mouths designed for
chewing. True bugs have long snouts
designed for sucking sap from plants.
Flies, mosquitoes, yellow jackets,
midges, and gnats often make it a habit
to bug people. The next time they start
bugging you, remember that they are
not true bugs at all. They are insects.
Tell them to “Bug Off.”
To learn more about the CAP LTER
Ecology Explorers program, contact
Monica Elser at 480.965.6046 or
Susan Williams at 480.965.1961.
E-mail to ecology.explorers@asu.edu.
Or,visit the Ecology Explorers Web site—
http://caplter.asu.edu/explorers/
C h a i n R e a c t i o n . 2 22
{A Pa i r o f D u n g B e e t l e s just making a living. They roll a ball of cow dung
to a burrow where they lay eggs. The dung will feed the grubs when they hatch.
Arthropods
aerate soil,
pollinate crops,
and do a
variety of other
essential jobs.
The Long-Horned Wood Boring Beetle male defends
saguaro fruits in order to mate with females attracted to the food.
John Alcock photos
B i r d s , b i r d s , b i r d s .
Phoenix is a city filled with birds.
Birds of many kinds. Birds of many colors.
Some of these birds are native to the Sonoran Desert. Some are
birds that have moved here to stay. And some are birds that are just
passing through on their way to nesting grounds in other locations.
How many different kinds of birds live in Phoenix? No one is sure,
for now. But lots of people are watching and counting birds to find
the answer. If you see a stranger lurking around your neighborhood
with binoculars at dawn, don’t be alarmed. Chances are, you’ve come
across a volunteer birdwatcher taking part in an important study.
The study is part of the Central Arizona-Phoenix Long-Term
Ecological Research (CAP LTER) project at Arizona State University.
Scientists in charge of the project want to find out what kind
of impact all the new building and development is having on bird
communities throughout the Phoenix metropolitan area.
About 90 local volunteers are helping to collect this information.
Armed with binoculars and notebooks, they walk through Phoenix area
neighborhoods at sunrise. They make note of all the birds they see or hear.
Joan Powers is a volunteer. “Initially I got stopped a lot,” she says.
“People get wary when you’re walking around with a clipboard and
binoculars at odd hours of the day.” Today, people living in the neighbor-hoods
patrolled by Powers recognize her. “I’ve been doing this for more
than a year,” she says. “Lots of people know me now. They ask, ‘What new
birds have you seen today?’”
“This study provides a unique opportunity to involve the public,”
says Mark Hostetler, a postdoctoral fellow at ASU who designed the
bird survey project. “The majority of the population lives in urban areas.
Urban areas are expanding dramatically. But we don’t really understand
them. Ecologists don’t really focus on urban areas. We’d rather hang
around in forests,” Hostetler laughs.
The main goal of the bird study is to establish
a pattern. Is that pattern consistent year after year?
What are the mechanisms causing the patterns?
For example, does housing density or road traffic
affect bird populations in Phoenix?
Volunteers typically study a one-kilometer area divided
into 10 segments. They make a note of all the birds they
can see or hear. Some professional birders also participate.
These bird-watching pros study four key habitats: golf
courses, new residential neighborhoods, older residential
neighborhoods, and desert remnants like Papago Park.
Cardinals love the Sonoran Desert.
Just like human "snowbirds," they
flourish in places where winters are
mild.
The Black-Headed Grosbeak
has a conical beak adapted for
crushing seeds.
Phoenix is one of two urban areas
selected for long-term ecological study.
The other city being studied is
Baltimore, Maryland. “Long-term” is an
important part of the study, according
to ASU scientists. Most studies like the
bird survey only last for a year or two.
CAP-LTER research, however, is funded
for at least six years.
Birds Phoenix: A City for the
By Diane Boudreau
23 http://chainreaction.asu.edu/
Robert Ohmart photo
Charles Kazilek photo
Wwhea t know
so far:
Most days, Powers sees about 15 of the
same basic kinds of birds. But spring migra-tion
often brings in some odder species.
ASU scientists hope to learn more about
migrating birds that stop to rest in Phoenix.
“Nothing is known about stopover ecology,”
Hostetler says. “We’ve seen lots of migrating birds
coming through. There are more birds in Phoenix than outside
the city. But the composition is different.”
The bird survey provides information that is useful to ecologists.
ASU researchers say early findings of the study are that building and
landscape design play a bigger role in attracting birds than zoning.
In other words, the style of buildings and the type of vegetation around
them matters more than whether they are houses, stores, or factories.
This information could help designers plan more bird-friendly neigh-borhoods.
Developers can use it to create communities that are more
attractive to birds. The researchers are even trying to connect with
realtors, encouraging them to use birds as a selling point.
ASU scientists think that involving the public is one of the best parts
of this project. Many of the volunteers are retired people. Children and
teachers from many local schools also help to collect information about
birds. Teachers are trained to lead their students in conducting point counts.
They stand in one place and count the birds in a 20-meter radius over
a certain time period. Then they send the data in to the kids’ section
of the CAP LTER Web site.
One goal of the project is to help connect urban
kids to their environment. When he gives talks
at schools, Hostetler often asks kids, “Where do
chickens come from?” Many of them will name
the local supermarket! “Urban life is great—
we have all these conveniences—but it’s
disconnected from nature. Understanding how
humans affect the environment can help us
minimize our impact.” Hostetler explains.
C h a i n R e a c t i o n . 2 24
Prairie Falcon
Cactus Wren
Redtail Hawk
Daryl Abbott /Southwest Wildlife
Rehabilitation Center
George Andrejko photos
George Andrejko photos
CAP LTER Bird Survey findings
Building and landscape design
play a bigger role in attracting birds
than zoning.
Escaped pet birds are thriving and
breeding throughout the Phoenix area.
“In my study area we have a population
of peach-faced lovebirds that has been
surviving and enduring. They obviously
escaped out of someone’s house,” says
Joan Powers. Peach-faced lovebirds are
native to hot, dry African habitats.
Arizona has all the comforts of home
for them. Unfortunately, these sweet
green birds with the rosy faces may pose
a threat to native Arizona birds. They are
potential competitors against wood-peckers
and other birds. The lovebirds
can take over giant saguaro cactuses.
Powers says that lovebirds aren’t the
only escapees she sees. Parakeets and
parrots have also shown up on her list.
Phoenix Bird Survey Study data
is available to everyone at
http://caplter.asu.edu/po12.
Visitors can learn exactly what species
live where. To learn more about
other CAPLTER projects visit
http://caplter.asu.edu/explorers/
25 http://chainreaction.asu.edu/
The Gil a Woodpecker is an
important part of the Sonoran Desert
animal community. Every spring,
male and female woodpeckers work
together to peck a deep hole in the
thick stem of giant saguaro cactus
or in the trunk of a cottonwood tree.
Elf Owls and other birds make their
nests in old woodpecker holes.
Lizards and spiders and insects of
many kinds also live in the old holes.
George Andrejko photo
Tim Trumble photo
Robert Ohmart photos
Anna’s Hummingbirds
live in the fast lane. To get the
energy they need for hovering,
hummingbirds must eat half
their body weight in sugar
each day. Some species beat
their wings as fast as 80 times
per second. Proportionally,
a hummingbird’s heart is
the largest of any animal.
Gambel’s Quail
is quite easy to recognize
by the black tear-shaped plume
on top of its chestnut brown head.
Gambel’s Quail has a loud, cackling
call that repeats three syllables.
The second syllable has the
highest pitch. The quail’s
ringing call is a true sound
of the Sonoran Desert.
Pyrrhuloxia gets its name
from Latin and Greek words meaning
"bullfinch with a crooked bill."
Northern Oriole has a clear, flute-like call.
It whistles single or double notes in short bursts.
Numbers
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N U M B E R S
A N D
B I O L O G Y
More than 1 quintillion insects–
1,000,000,000,000,000,000–
live on Earth on any given day. By 2000,
there were a little more than 6 billion
humans—6,000,000,000.
Scientists have discovered and
described more than 900,000 different
kinds of insects—more than 75 percent
of all the known animals on Earth.
There may be as many as 30 million
more kinds of insects yet to be
discovered.
There are more than 30,000 known
species of spiders. About 2,500 kinds
of spiders live in North America.
The not-so-magic tool they use is called statistics.
Statistics is a type of mathematics used to organize and understand data.
Data are figures and symbols. Data include all the raw, unprocessed facts
that scientists gather during their experiments and measurements.
Scientists use statistics to give meaning to all these raw facts and
numbers. Statistics help scientists describe how things are right now.
They also help to make predictions about how things will be in the future.
For example, ASU professor Harvey Pough wanted to know if he could
help desert tortoises grow up faster by feeding them high-protein diets
(See story, page 22). He started with 24 tortoises. Half were fed a protein diet
and half a salad diet. Then he weighed all of the tortoises. The result was
12 different numbers for each tortoise group.
Pough used statistics to find out the average weight of tortoises in each
group. He found that tortoises on the protein diet weighed an average
of 800 grams. But tortoises in the salad group weighed an average of only
360 grams. Those results gave Pough an answer—the protein tortoises were
definitely growing faster.
Statistics are especially useful when you need to learn about huge groups
of subjects. For instance, ASU scientists working on the Central Arizona-
Phoenix Long-Term Ecological Research project want to know
how urban development and land use affects the number of bugs in Phoenix
(See story, page 20). But they can’t possibly count every single bug in all
of Phoenix—it would take them forever! Instead, the scientists carefully
chose a few sections of Phoenix to study. They count all the bugs
in those small areas. The areas they chose are called a representative
sample because, added together, all the areas represent the whole city.
The scientists make lots and lots and lots of measurements. Then they
use statistics to find out what their sample says about the whole population
of bugs in Phoenix. For example, if they find 47 beetles in their park area
sample, they can estimate how many beetles there are in all Phoenix parks.
John Wallace is a 9th grade teacher at Mountain Ridge High School. His
students used statistics to find out whether urban development has affected
the number of bruchid beetles and palo verde trees in their school district.
Bruchid beetles lay their eggs on the seedpods of palo verde trees.
The eggs hatch into larvae, which burrow into the pods and eat the seeds.
The larvae grow inside the pods and come out as adult beetles.
Wallace’s students collected seedpods from trees in their school district
and from trees in a rural area outside Phoenix. They studied the rural area
to get an idea of how things were before their school district was devel-oped.
The students counted the number of pods found in each area, and
the number of beetle holes in each pod. The beetle holes told them how
many beetles were born.
C h a i n R e a c t i o n . 2 26
Tell The
Story…
Sometimes.
Scientists try to
answer questions about
the world around us.
That is their job.
To do this, they design
experiments and make
lots of measurements.
The result of all this work
is usually a long list of
numbers. So how exactly
do scientists turn all
those numbers into
meaningful answers?
by Di a n e B oudr e au
27 http://chainreaction.asu.edu/
T r a p 1 T r a p 2 T r a p 3 T r a p 4 T o t a l
Thought Question
Scientists are not the only people
who use statistics and graphs. In fact,
statistics are used in almost every part
of life. Your teacher uses statistics
to come up with your average grade.
Political polls use statistics to predict
who will get elected president.
Where else can
you see statistics
in use?
1 6 10 2 1 1 20 2 4 8 7 0 3 0 11 0 9 15 48 4
S p i d e r s
B e e t l e s
A n t s
C r i c k e t s
The findings for inside and outside the city were different. Using statistics,
the students learned that this difference was significant—it was a real effect
of urban development, not just random chance.
But were there more or less pods and holes inside the city? The answer
was surprising.
There were more seeds inside the city than outside, probably because
city trees are well irrigated. But what about the beetles?
“If all you had was the seed data you might think there would be more
beetles, because the beetles eat the seeds,” says Wallace. “In fact, we found
more holes per pod in the wild sample.”
After researchers analyze their data with statistics, they need to share
it with other people. One of the easiest ways to do this is by creating
a graph. Graphs take statistical information and make it into a picture.
People looking at the graph can understand the data at a glimpse.
Let’s look at an example. Suppose a scientist was catching bugs in four
different traps. On one particular day he counted the following bugs:
Trap 1: 1 spider, 6 beetles, 10 ants, 2 crickets
Trap 2: 1 spider, 1 beetle, 20 ants, 2 crickets
Trap 3: 4 spiders, 8 beetles, 7 ants, 0 crickets
Trap 4: 3 spiders, 0 beetles, 11 ants, 0 crickets
Now look at the graph below.
Which way of showing the data
gives you a better understanding
of what the scientist found? Why?
Woodley is a biology doctoral student
at Arizona State University. Her scientific
instincts overrule her instincts as a hiker.
That’s why she sits quietly in the forest.Woodley
accepts the risks in order to study the aggression of
female mountain spiny lizards.
For the past three years, Woodley has studied the behavior of these five-inch-
long reptiles. She collects blood samples to study their hormones and
observes the animals to see how they behave.
Lots of mountain spiny lizards live along the wood-lined creeks of Arizona
mountains like Mt. Graham. The lizards are good candidates for scientific
studies because they are easy to watch and easy to catch. Both male and female
mountain spiny lizards are intensely territorial. They do furious pushups that
send the message, “Here I am! Don’t come into my territory!”
At least that is Woodley’s interpretation of lizard body language.
Woodley studies how hormones inf luence female aggression
in mountain spinys. Female mountain spinys are more aggressive than
females of other lizard species. They will defend their territories by
displays of pushups or by extending their dewlaps (throat f laps).
They also charge and bite intruders. In male animals, the hormone
testosterone leads to aggression. But scientists don’t know why many
females also behave aggressively, Woodley says.
During her last field study, Woodley worked in a forested area about
6,000 feet up the side of Mt. Graham. The mountain is located in the Coronado
National Forest about 60 miles northeast of Tucson. Mt. Graham is black bear
country, and Woodley has seen her share. The hiker in Woodley knew that
she was supposed to make noise to scare them away. Scientist Woodley had
to remain silent.
Thought Question:
In what other groups
of animals do the females
compete for food and territory?
Hormones are chemical messengers
produced by endocrine glands.
They travel through the bloodstream
to reach different parts of the body.
When they reach their destinations,
hormones give instructions for
controlling growth, metabolism,
sexual reproduction,
and other body processes.
Learn more about hormones
and lizard behavior—
Visit the website at
http://askabiologist.asu.edu
/research/tlizards
B I O L O G Y
A N D
C H E M I S T R Y
C h a i n R e a c t i o n . 2 28
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A good hiker visiting
Arizona’s 10,717-foot
Mt. Graham would make
plenty of noise to frighten
bears away. Backcountry
visitors would steer clear
of javelinas and rattlesnakes
to avoid provoking them.
And no one would risk
attracting lightning by
carrying a metal fishing pole
along a mountain trail
during monsoon season.
No one except Sarah Woodley,
that is.
Following the Fighting Females
by Dennis Durband
She was more wary of the javelinas—because of their sharp canine
teeth—and the “jumpy” cattle that graze through the forest.
Snakes often ate her lizard
subjects while she was
studying them.
Monsoon thunderstorms
filled the sky late in the afternoons.
Woodley got soaked many times. Despite the
attractions and distractions, she made her obser-vations
and collected 60 female spiny lizards over
a seven-week period.
In a laboratory at ASU, Woodley performed
surgery on each of her captured reptiles.
She removed some of the lizards’
ovaries—glands that produce
eggs and female hormones.
She gave others a testos-terone
implant.
A second group of lizards served as controls.
The control group underwent fake surgery. Woodley
didn’t remove or implant anything on these lizards.
None of the lizard surgeries harmed the animals.
They were put to sleep so they didn’t feel any pain. Surgery only lasted about
15 minutes, and all of the lizards survived. Each patient went home the day
after surgery. Each was marked with a harmless paint stripe for identification.
Woodley says the lizards acted skittish for several days. So she waited three
weeks before making new behavioral observations. During those three weeks,
she visited the site every other day to help the lizards get used to her presence.
Woodley watched to see how the surgically altered females reacted to
intruders. She used a fishing pole and dental f loss to place intruders on rocks
in the territories of other females.
Females without ovaries showed a decrease in aggression. Since ovaries are
the main source of the hormone estradiol, Woodley believes that estradiol
plays some role in aggression. However, the female lizards with testosterone
implants rated high in displays but low in charging intruders. The testosterone
wore off over time. Woodley thinks the hormone may have caused females
to exhibit male-like courtship displays.
Fake surgery did not seem to change the lizards’ behavior. More than
70 percent of those females charged and bit intruders as usual.
Woodley’s research is important because most scientists have assumed that
aggressive competition is a characteristic of males. They have ignored the large
number of situations where females aggressively compete.
What is a
Control Group?
Control groups are an important part
of many scientific experiments.
Researchers use control groups to find
out if a treatment really has an effect.
Sometimes, study subjects act differ-ently
after treatment just because they
know they got treated.
Suppose that you go to your doctor
and tell her that you can’t sleep at night.
She gives you a pill to help. You go
home, take the pill, and fall right to
sleep. The pill did the trick, right?
Maybe. Or, maybe you believed the
pill would work, so you quit worrying
about falling asleep. You got so relaxed
you had no trouble sleeping. It was
your state of mind, not the pill itself,
which helped you.
The way to find out what really worked
is to conduct an experiment using a
control group. In this type of experiment,
about half of the subjects would receive
the real sleeping pill. The rest would
receive a fake pill, usually made of
sugar. The fake pill is called a placebo.
None of the subjects would know which
pill they got.
After the experiment, the researcher
would compare the results. If the
people taking the real pill fell asleep,
but the control group didn’t, then we
woould know the pill works. If both
groups fell asleep, then we would know
that the act of taking the pill, not the
pill itself, was what worked. This is
known as the “placebo effect.”
Even animal researchers often need
to use control groups. For instance,
Sarah Woodley wanted to know if
removing a lizard’s ovaries would change
the lizard’s behavior. She needed to be
sure that the loss of ovaries, not the
experience of capture and surgery, was
what caused any change. Woodley used
a control group of lizards. The “control”
lizards went through surgery, but kept
their ovaries.
Can you think of some reasons why
a lizard might be less aggressive after
surgery, even if the surgery is not quite
the real thing? —Diane Boudreau
29 ht tp://chainreact ion.asu.edu/
Thermoregulation:
The management of body heat is called thermoregulation.
Without proper thermoregulation, animals cannot survive. To understand
thermoregulation, it is important to know a little bit more about heat.
In the 1700s, scientists thought of heat as a mysterious f luid, which they
called "caloric." They thought that heat f lowed froma hot into a cold substance
in the same way water flows from a full into an empty cup. For more than
100 years, the caloric idea helped to explain observations about heat.
Ideas changed in the mid-1800s. New observations about heat could
not be explained in terms of the caloric idea. Today, heat is just one part
of the modern theory of thermodynamics. The theory says that heat is
a form of energy, not a mysterious f luid. But we still say that heat "f lows."
Scientists know that heat inf luences temperature. When a substance
contains lots of heat, it is hot. When it contains little heat, it is cold.
The amount of heat in a substance is called its heat content. When a hot
substance is put in contact with a cold substance, both substances eventually
become warm. They reach a state called “thermal equilibrium.” Heat from
the hot substance f lows into the cold substance until it is balanced
between the two. As a result, both substances reach the same temperature.
That temperature stays the same over time.
If left alone, heat always f lows from hot to cold. This is the direction
of spontaneous f low. “Spontaneous” means that the f low happens all
by itself. No usable energy is consumed.
Substances or materials often come in contact with one another.
During that contact, heat can f low from one substance to the other.
This process is called conduction.
Any substance, including the skin, feathers, or fur of desert animals,
is always in contact with its surroundings. That substance is always exchanging
heat with those surroundings. If heat is added faster than it is lost, the heat
content and temperature of that substance will increase. If heat is lost faster
C h a i n R e a c t i o n . 2 30
The Wright
Stuff
BY DAVID WRIGHT
Hot
Enough
For You?
The caloric idea lasted
as an explanation for heat
because it described many
commonly observed effects
of heat.We now know
that heat is the energy
of moving molecules.
This explains the most
careful observations we
can make of heat effects.
The molecules in liquids
and gases bounce off each
other like bumper cars.
The molecules can’t move
around in solids. They
vibrate in place, as if held
together by tiny springs.
Animals of all kinds
live in hot, dry South-western
deserts.
These creatures have
adapted to survive
sizzling summer days
and frosty winter nights.
To stay cool, a desert
animal must avoid
and shed heat. To stay
warm, the creature
must gather and store
heat in some way.
than it is added, heat content and temperature will decrease. If heat is added
and lost at equal rates, the heat content and temperature will not change.
Every substance has a different ability to hold heat. This ability is called
the heat capacity of the substance. Different substances have different heat
capacities. As a result, they can have different heat contents, even though
they may exist at the same temperature.
Imagine that heat really is f luid and that a substance is a cup. The diameter
of the cup represents its heat capacity. The amount of f luid in the cup is the
heat content. The height of the f luid in the cup represents the temperature.
The desert is hot because the soil absorbs heat from intense sunlight.
This is called radiant heating. Sunlight is a form of radiation that contains
many different kinds of light, including infrared light. Infrared light carries
heat and is not visible to the human eye.
Perspiration is efficient for cooling,
but only if the air is dry. If the air is
humid, the evaporation process is slow.
Heat is not removed quickly. Unfortu-nately,
perspiration requires a large
amount of water, which usually
is scarce in the desert.
Many desert animals do not have
sweat glands. Birds and rodents, like
dogs, must pant to cool themselves.
When they inhale dry air, water found
on the linings of the lungs evaporates.
The evaporating water absorbs heat
from the lungs. Heat is exhaled along
with the water vapor. But if these
creatures become dehydrated,
they will overheat.
This is what sweat looks like on the surface
of your skin—enlarged thousands of times by
electron microscope. The image was made from
a latex rubber mold of a fingerprint. Living things
cannot be viewed in an electron microscope because
the energy of the electron beam used to illuminate
the subject would fry it!
31 http://chainreaction.asu.edu/
H e a t c a p a c i t y
L o w H i g h
Heat flow from warmer to cooler
T e m p e r a t u r e
The same heat content can result in different temperatures,
depending on the heat capacity of the substance.
Examples of average
body temperatures
Birds: 100-112° F
Rabbits, sheep and cats: 102.2° F
Horses: 100.4° F
Whales: 95.9°F
Humans: 98-99° F
(in America and France, “normal”
is set at 98.6°. In Great Britain,
98.4° is considered the normal point).
Some mammals hibernate
in the winter and drop
their body temperatures
during this time. The most
extreme example is the
Arctic ground squirrel,
which can drop its body
temperature to 28.4° F
while it hibernates.
C h a i n R e a c t i o n . 2 32
Conduction from the desert soil causes the air to get hot. The air expands.
As it becomes less dense and more buoyant, the hot air rises. To replace
the rising hot air, cooler air from above sinks to the desert f loor. That air
then absorbs heat and the cycle continues. When heat moves because hot air
rises and cool air sinks, the process is called convection.
Desert animals have adapted ways to stay cool during the hot desert day.
They stay in shade or find a cool place underground to avoid radiant heating
and conduction fromthe soil.Most desert animals are nocturnal,whichmeans
they are active only at night. This is thermoregulation through behavior.
Thermoregulation also depends on the way in which heat inter-acts
with matter. Substances can exist in solid, liquid, or gas form.
The form, or phase, of a specific substance is determined
by its heat content. Think about water. If ice absorbs heat,
it will melt to form liquid. If the liquid absorbs heat, it will
evaporate to form steam or vapor. However, if that water
vapor loses heat, it will condense to form liquid. If the liquid
loses heat, it will freeze into ice.
The change between phases is called a transition. For animals,
evaporation is an important process for cooling—melting, freezing, and
condensing are not practical methods for thermoregulation.
For example, if an animal has enough water in its body, it can use
evaporation to stay cool by perspiration (sweating) and respiration (breathing).
Animals with sweat glands perspire to cool large areas of skin. Water is
secreted through pores in the skin. When it evaporates, the water vapor
carries away heat from the skin.
Lizards, snakes, and other cold-blooded animals cannot generate body
heat from the energy in their food. To stay warm, they absorb the heat they
need from the surrounding environment. They absorb heat directly from
sunlight. They also use conduction to absorb heat from the hot desert soil.
They retain that heat by insulation.
Coyotes, javelinas, rodents, birds, and other warm-blooded desert animals
also absorb external heat. But they also use chemical energy from food
to generate large amounts of internal body heat.
As long as food is plentiful, warm-blooded animals have a distinct
advantage for thermoregulation. Warm-blooded animals can stay warm
even when it is cold outside for long periods of time. On the other hand,
cold-blooded animals don’t need as much food to survive extreme
temperatures because these creatures don’t use the energy from their
food for thermoregulation.
i n s u l at o r s
Temperature is
a measure of heat.
There are several
different temperature scales.
The Fahrenheit scale is the oldest
system for measuring temperature,
still common in the United States.
ItwasinventedbyGermanphysicist
named Daniel Gabriel Fahrenheit
in 1724. He set the freezing point
of water at 32 degrees, and the
boiling point at 212 degrees.
Anders Celsius invented the Celsius
scale in 1743. He set the freezing
point of water at 0 degrees and
the boiling point at 100 degrees.
This system is now used in most
countries and among scientists
everywhere. It is also called the
Centigrade scale.
The Kelvin scale measures the ultimate extremes
of temperature. It was invented in 1848 by Lord
William Thomson Kelvin. In the Kelvin system,
zero degrees — or “absolute zero” — is the
temperature at which there is no molecular
motion and therefore, no heat at all. There is
no temperature colder than absolute zero.
Absolute zero is equal to -273 degrees Celsius
or -460 degrees Fahrenheit.
Heat flows quickly through some
substances. These are called thermal
conductors. Heat flows slowly through
substances that are thermal insulators.
The flow of heat into or out of a substance
depends on conduction. The storage of heat
depends on insulation. Thermoregulation
depends on both conduction and insulation.
Substances that are good thermal conductors:
metal or water.
Substances that are good thermal insulators:
wood, bone or rock.
What characteristics of these materials
affect heat flow?
Desert birds, like this turkey vulture, often soar
effortlessly for hours by riding on thermals,
the updrafts of rising air created by convection.
By gliding on thermals, the birds conserve
precious energy as they hunt for food.
c o n d u c t o r s

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O nc e h o m e t o t h e f e w and heady,
the southwestern United States has experienced
a population explosion in recent years.
For example, Phoenix, Ariz., is home
to more than 1 million people, making
it the nation’s seventh largest city.
Surrounding cities, from Scottsdale to
Las Vegas, have also traded cactus blooms
for population booms. That trend may
spell the doom of desert tortoises.
Desert tortoises once roamed freely
throughout southwestern California, southern
Nevada, and western Arizona. Today they are in trouble.
The sad truth is that tortoises do not stand a chance against cars. Hundreds of
the animals are crushed every year by cars or off-road vehicles. Pet tortoises
released into the wild provide a new danger. These animals often take back
deadly diseases to the wild.
That story is the same throughout the world. Tortoise populations in
Africa, Asia, and South America shrink as human populations grow.
A group of researchers from The Phoenix Zoo and Arizona State University
is working to give tortoises a head start on their reproduction. A goal of their
Desert Tortoise Project is to help tortoise hatchlings grow up faster by chang-ing
their diets. This will let the animals lay more eggs during their lifetimes.
“For many tortoises, survival of the species is now a numbers game,”
explains ASU biologist Harvey Pough. “Each female must produce
at least two offspring who survive to produce just to keep the
population size stable.” That job is tougher than it sounds.
In the wild, desert tortoises do not reach sexual maturity—
when they can produce babies—until age 20. They then lay,
on average, three to seven eggs per year—which often get
eaten by coyotes, snakes, and Gila monsters. Very few
tortoise hatchlings survive their first year or two.
“A baby turtle is just an Oreo cookie to a predator,”
says Pough, a professor of Life Sciences at ASU West.
“The death rate of juveniles is about 95 percent
before age five.”
Pough and his team are testing a diet developed
by scientists at the National Zoo in Washington, D.C.
Those scientists found that desert tortoises grew
faster when they ate high-protein diets instead
of greens. They grew to full size in just five
years instead of the typical 20 years.
Speeding
by
Danielle Brooks
Slow and steady,
the fabled tortoise
eventually out-raced
the hare.Times have
changed. Today, the
desert tortoise is in
a race for its very life.
The competition—
smarter and much more
brutal—is human beings.
What is the difference between a turtle
and a tortoise? A tortoise is actually
one type of turtle that lives on land.
Unlike other turtles, tortoises only
go to water to drink or bathe.
The Desert Tortoise can live in places
where the ground temperature gets
above 140°F. It digs underground
burrows to escape the heat.
A desert tortoise spends at least
95 percent of its life in burrows.
C h a i n R e a c t i o n . 2 2
Tortoises
The National Zoo study did have a weakness. Many of the subject
tortoises were captured in the wild. As a result, no one knew their exact ages.
The ASU/Phoenix Zoo study fixes that problem by using only animals
whose age is known.
Researchers started in August 1995 with 24 hatchlings. They divided the
tortoises into two treatment groups. One group was fed a traditional zoo
salad diet. The second group got high-protein pellets as food.
Tortoises in the high-protein group were switched from zoo salad to
the experimental food. They had to be taught how to eat pellets. At first,
researchers ground the pellets into a powder and sprinkled it on the tor-toises’
greens. They were slowly weaned off the salad onto straight pellets.
The process took until March 1996.
By November 1999, tortoises in the protein group weighed about
twice as much as tortoises that ate salad. The average pellet-eater weighed
in at a hefty 800 grams, compared to 360 grams for the salad group.
The tortoise hatchlings in the
Desert Tortoise Project were placed
in quarantine for a month to ensure
a disease-free start. Tortoises from
different families were divided equally
between the study groups. This allowed
the researchers to factor in family
differences that might otherwise
affect the results. Like human families,
some tortoise families are naturally
bigger than others no matter what
they eat.
The sharp, serrated jaws of the
Desert Tortoise look a lot like a bread
knife. The jaws are perfect for shredding
tough grass and thick, pulpy cactus pads
and blossoms. The tortoise gets water
from its food and can store a month’s
supply in sacs under its shell.
3 http://chainreaction.asu.edu/
What do
desert tortoises
eat in the wild?
George Andrejko photo
“
”
This is the first time The Phoenix Zoo has participated in a collaborative,
scientifically based research project, according to Mike Demlong, the zoo’s
curator of ectotherms, or cold-blooded animals. “This study is helping the
zoo staff become better scientists,” Demlong says. “That is important, because
zoos aren’t just about fun and recreation anymore. We’re centers of conser-vation
and research. As such, we’re about building connections between
an increasingly urban population and the natural environment that
people are becoming more and more distant from.”
He says that the Desert Tortoise Project “is about inspiring
people to live in ways that promote the well-being of the nat-ural
world—even if it’s as basic as helping people understand
why they should try to avoid running over tortoises with
their all-terrain vehicles.”
Demlong says The Phoenix Zoo has dedicated special
summer and winter habitats to the Desert Tortoise Project, as
well as a total of about $300 per tortoise per year in food, facili-ties,
and veterinary care. “That’s a big investment for the zoo, given
that we receive no government funding. But it will be money well spent
if we can gain clear, conclusive data concerning the proper protein and
fiber diet ratios for head-starting healthy, high-quality tortoises,” he adds.
Demlong defines healthy as being free from all diseases—especially
respiratory disease and a common shell abnormality called “pyramiding.”
Pyramiding has been linked to other high-protein diets. As yet, it has not
affected The Phoenix Zoo tortoises.
Demlong defines high-quality tortoises as those able to forage, dig burrows,
avoid predators, and generally behave like tortoises in the wild. That is
important, he says, or else head-started tortoises will never be released.
ASU’s Pough agrees. “The real question is, even if the project’s ‘superju-veniles’
reach adult size within five years, will they be physiologically and
behaviorally mature? Will we have ‘young adults’ or ‘big babies’?” he asks.
This is the point where Ellen Smith enters the story. A scientist at ASU
West, Smith studies tortoises of the original National Zoo group at the Desert
Tortoise Conservation Center in Las Vegas. Those tortoises are now between
nine and 13 years old. Smith’s work focuses on social behavior and hormones.
Smith and her Las Vegas colleagues began by pairing up each superjuvie—
or head-started tortoise—with an opposite sex adult. Then they watched.
Tortoise “dating” behavior is a pretty strange sight. Normal adult tortoises
do a lot of nose-to-nose sniffing. Males “bob” their heads during courtship
and bite at the front legs of females. Females show their willingness to mate
by staying still. Otherwise, they just walk away.
The research group in Las Vegas watched to see if the superjuvies
showed these adult behaviors. They collected blood samples to compare
ASU scientist Harvey Pough says
tortoises play a unique role in the
desert. They are big and strong enough
to dig burrows in the tightly compacted
desert sand. Coyotes, snakes, lizards,
toads, insects, and mice all use
abandoned tortoise dens for their
own retreats. Tortoises dig burrows
throughout their 40 to 50 acre
ranges. Without them,
other creatures would
be at the mercy of the
desert’s extreme
temperature swings.
Scientist Smith glues a tiny plastic
identification tag to a hatchling.
If superjuvies could
reproduce at age five,
that would be four times
faster than in the wild.
That would be a clear
head start.
Ellen Smith
C h a i n R e a c t i o n . 2 4
John C. Phillips photos
“
”
hormone levels of the superjuvies to levels in adults. Adults that are
ready to reproduce have higher levels of sex hormones in their blood than
immature tortoises. The scientists also studied all eggs that were laid to find
out whether those eggs were fertile.
All the eggs from 1996 did hatch. Most female superjuvies did not lay any
eggs; the few eggs they did produce never hatched. Male superjuvies, on the
other hand, were able to successfully fertilize their adult partner’s eggs.
“Right now, I’d say superjuvie males appear mature while the females
seem unable to reproduce,” Smith says. “But not knowing the exact age
of the National Zoo tortoises makes interpretation difficult.”
Smith and the Las Vegas group will continue watching the female super-juvies
from the National Zoo to see when they begin to reproduce success-fully.
However, researchers expect data from the Phoenix study to answer
more questions because age, family relationships, and hibernation history
will all be known.
“Obviously, our ultimate hope is that superjuvies reach sexual maturity
at the age of five or six, and that the females continue producing
eggs until age 60 so they can help restore the population,”
Pough says. “The desert tortoise is a very important
species in the desert habitat.”
If we really can head-start
tortoises so that
they reach adult size in
five years or less, captive
breeding and release
programs for endangered
species may be possible.
We hope this method can
be used to head-start
other tortoise species
that are more endangered
than desert tortoises.
H a r v e y P o u g h
Desert tortoises lay eggs in May,
June, and July. An adult female might
lay four to eight eggs in a clutch.
She can produce two or three clutches
each season. Experiments have shown
that when tortoise eggs are incubated
at cooler temperatures (79-87°F),
they produce all male tortoises.
Warmer temperatures (88-91°F)
produce all females.
Male desert tortoises often fight
each other. The weaker male usually
runs away.
The desert tortoise stays cool inside
deep burrows that it digs in tightly
compacted desert gravel.
In order to get enough drinking water
in a dry climate, desert tortoises dig
basins in the soil to catch rainfall.
The Desert Tortoise Project is
a collaboration between ASU and
The Phoenix Zoo. For more information,
contact Harvey Pough, Ph.D.,
ASU West, 602.543.6048.
E-mail at Pough@asu.edu.
Or contact Mike Demlong at the
Phoenix Zoo, 602.914.4373. E-mail at
Mdemlong@phoenix-zoo.org
5 http://chainreaction.asu.edu/
Wh a t i s t h e b e s t w a y t o a t t r a c t g i r l s ?
A bright orange tail can help. It helps a lot if you are a chuckwalla
living among the rocks on South Mountain in Phoenix, Ariz.
Matthew Flowers is a graduate student at Arizona State
University. He studies chuckwallas. He wants to determine if
South Mountain chuckwallas are a brand new species of lizard.
Lots of chuckwallas live on South Mountain. In fact, within
the park’s boundaries, the concentration of chuckwallas is five
times higher than the normal density found in Southwestern
deserts. If you go chuckwalla hunting, you might find as many as 60
of the big lizards living in every hectare of territory.
Chuckwallas are big lizards. They grow to almost a foot in length and can
weigh as much as 12 ounces. They are the second largest of the 38 lizard species
found in Arizona. Gila monsters are the biggest. The average life expectancy
for a chuckwalla in the wild is 10 to 15 years, but some of the big lizards live
20 to 25 years.
“South Mountain Park contains a unique population of chuckwallas,”
Flowers says. “When I first arrived, the question was whether or not the
South Mountain population should be considered a new species of lizard.”
The Arizona Game and Fish Department currently protects the South
Mountain chuckwallas from collectors. The department supports Flowers’
research effort. The ASU scientist observes and collects live specimens.
Chuckwallas have very distinct color patterns. The colors provide an ideal
trait for studying the big lizards. Male chuckwallas often have different colored
tails. The typical tail color is white. Some have black tails. South Mountain
chuckwallas are unique. The entire tail on most males is bright orange.
Flowers converted his Tempe backyard into a chuckwalla enclosure.
He wants to know if female chuckwallas prefer one color tail to another.
To find out, he paints the tails of males. Then he tests specimens within
a population or between populations.
Brian Sullivan is an evolutionary biologist and ASU West professor.
He also is one of Flowers’ advisers. “Matthew's study of geographic variation
in chuckwalla mating behavior has generated widespread interest among evo-lutionary
biologists,” Sullivan says. “He is providing new understanding of
how environmental factors can shape differences in the behavior of males and
females of a species.”
Flowers makes behavioral observations on South Mountain during
all seasons, including the sweltering heat of an Arizona summer.
“We do focal animal observations,” Flowers explains. “We pick an animal,
watch it for half an hour, and then record its behavior. For example, I watch
the males fight. Then I mark down the color patterns of the winner.”
Chuckwallas are secretive reptiles. It takes time to gather enough data
ofTails
C h a i n R e a c t i o n . 2 6
Tales
of Tails
by
Dennis Durband
and Conrad J. Storad
South Mountain Park in Phoenix is
the largest municipal park in the world.
It covers 16,500 acres. The park features
unique geology and is home to many
different kinds of plants and animals.
Matt Flowers tracks chuckwallas in the
park with the aid of spotting scopes and
radio direction-finders.
A hectare is equal to 10,000 square
meters. How big is that? Two football
fields side by side would cover nearly
one hectare. If you went looking for
chuckwallas in other parts of Arizona,
you could expect to find about a dozen
chuckwallas per hectare.
about individual animals. Flowers says that the battles between male
chuckwallas can be an amazing spectacle.
“They lock jaws and roll around on the desert f loor,” he explains.
“Chuckwallas also make interesting social displays. Fighting is the ultimate part
of social interaction between the males. But they will try to solve issues before
fighting. They puff up their bodies and go through other physical displays,
including what appears to be a series of rapid pushups.”
Flowers logs his observations into a computer database. He uses the
computer to compare behavior, such as the number of pushups done among
individual chuckwallas over a certain time period.
Catching the big lizards can be painful. Flowers might spend anywhere
from five to 90 minutes trying to collect a single lizard. Chuckwallas retreat
from danger by wedging into rock crevices and inf lating their bodies. A well-entrenched
lizard can win the tug of war, forcing the frustrated scientist
to retreat, bloody fingers his only reward.
On South Mountain, female chuckwallas seem to prefer
males with orange tails to males with white tails.
“This suggests that they will only mate
with males from their own population,”
Flowers explains. “It also suggests that they
might be a different species. The fact that
South Mountain females prefer bright orange
tails over dull orange tails tells us more.”
Flowers says that orange tails may indicate the quality of a male chuck-walla’s
territory. The orange color is based on carotenoid pigments absorbed
from plants eaten by the individual lizard.
Chuckwallas also have good chemical senses. Tiny differences might
determine which male a female will select for mating.
“There probably are many factors that affect mate choice by female
chuckwallas,” Flowers says. “Male tail color is just one.”
There are 38 lizard species
found in Arizona.
Chuckwallas are the second
largest kind of lizards in Arizona.
The Gila Monster is number one.
What is a species?
There are millions of different living
things, or organisms, on the Earth.
Biologists have a system for naming
these organisms by grouping them into
categories. The categories allow people
to talk about the organisms and study
them in a logical way.
A species is one of the categories that
biologists use. A species is a group
of closely-related
organisms that
can breed together
and produce
offspring.
A Siamese cat
and a Russian blue
cat can breed and
have kittens.
Therefore, they
belong to the
same species. A Siamese cat and
a jaguar cannot breed—they are two
different species of cat.
It’s easy to see how a housecat and
a jaguar are different, but sometimes
the lines between species are blurry.
For example, sometimes people breed
different species of plants together
to produce hybrid crops. Even though
these plants are made to reproduce,
they still belong to different species.
The system isn’t perfect, but it has
been extremely useful for naming
and classifying life on Earth. So far,
scientists have found about 1.5 million
different species of animals, plants,
fungi, and microorganisms on our
planet.—Diane Boudreau
The Arizona Department of Game
and Fish support chuckwalla research
at ASU. For more information, visit
the ASU Research Magazine Web site—
http://researchmag.asu.edu
7 http://chainreaction.asu.edu
John C. Phillips photos
C h a i n R e a c t i o n . 2 8
AT HOME IN THE [Sonoran
C A T A L Y S T S Desert
make things happen.
They speed up reactions
and make some ingredients combine
that could not without them.
b y C o n r a d J . S t o r a d
Th e R e g a l H o r n e d L i z a r d
is active during the hot desert day.
It uses its tongue to slurp up ants.
George Andrejko photos
Space Shuttle astronauts in
orbit photographed the heart
of Sonoran Desert near Yuma, AZ.
B A J A C A L I F O R N I A
M E X I C O
A R I Z O N A
Phoenix
C
C
Hermosillo
T h e S o n o r a n D e s e r t i s
a n a r i d , r u g g e d p l a c e .
It also is a beautiful place filled with plants and animals.
Many of these animals and plants are unlike any other
creatures living on the Earth today.
The Sonoran Desert covers a large region of more
than 100,000 square miles. It spreads across north-western
Mexico, includes the Baja peninsula, and
covers the southeastern tip of California. To the north,
it stretches over a large section of southern Arizona.
The Sonoran Desert is a young desert. Scientists say that it has
existed in its current form for less than 10,000 years. It is very hot and dry
most of the time. Rain falls on a somewhat regular basis twice each year,
usually during the early summer and again during the winter.
Rain often falls all at once in violent storms streaked with lightning.
Sometimes rain does not fall at all for many months. Total rainfall
may amount to only seven to 10 inches in an entire year.
The Sonoran Desert is a living desert. It is not a sea of sand
and rocks. There are sand dunes, but only in a few areas. There
also are marshy, oasis-like areas called bosques, which form near
natural springs. Water in the desert means life. The Sonoran Desert
has water in the form of streams and washes from time to time.
But water does not often stay around for long.
9 http://chainreaction.asu.edu
Except for the tropical
rainforests of South America
or Africa, the Sonoran Desert
is home to more kinds of plants
and animals than any other
area of its size. These plants
come in many shapes and sizes.
So do the animals and insects.
T h e D e s e r t Wo o d R a t is also
called the Pack Rat. The rodent uses stones,
sharp sticks, and cactus spines to protect
the entrance to its burrow.
T h e A m e r i c a n
K e s t r e l is the
smallest falcon in
North America.
T h e D e s e r t
I g u a n a is active
at temperatures as hot
as 115 degrees. It can
grow more than a foot long.
P i p e v i n e Swa l l ow t a i l
male butterflies claim and defend
perches on ridges and hilltops
to keep watch for females.
The Saguaro C actus is the giant of the
Sonoran Desert, the only place it grows in the wild.
John Alcock photo
Tim Trumble photo
Desert plants are adapted to survive and f lourish
in hot, dry conditions. The roots are shallow nets or
deep straws that slurp up as much moisture as possible
following a rare rainstorm. Most have small waxy leaves
or sharp spines.
The Sonoran Desert’s animals and insects are just as tough.
Many desert mammals and reptiles are active only at dusk and
again at dawn. For this reason, it is rare for humans to meet
a javelina, jackrabbit, Gila Monster, or rattlesnake while
hiking during the day.
Bats, many snakes, most rodents, foxes, coyotes,
skunks, and other large desert mammals are
totally nocturnal. They sleep in a cool cave,
den, or burrow during the hot desert day
and hunt at night when the temperature
is cooler. Many desert birds are active during
the day. But they always perch in the shade.
Desert toads actually sleep most of the summer. They stay dormant deep
underground in moist soil until the summer rains fill the ponds. When they
emerge, they find mates and lay eggs quickly. The toads spend lots of time
eating and drinking to replenish their body reserves of food and water
for another long period of sleep.
Desert animals have developed many different ways
to find precious water. Some never drink water at all.
They get all the moisture they need from the plants
or insects they eat. The kangaroo rat and other
amazing desert rodents can actually make their own
water from the digestion of dry seeds. They will not
drink water, even if it is available by the bowlful.
C h a i n R e a c t i o n . 2 10
The Gila Monster is the largest and only venomous lizard found in
the United States. The big lizard’s teeth look like tiny grooved daggers.
Despite a fierce reputation, Gila Monsters actually are quite shy.
They spend most of the their time hiding in desert burrows
stolen from mice, squirrels, or other small rodents.
George Andrejko photos
Desert animals
have adapted
to live in hot,
dry conditions.
Can you explain
ways creatures
survive in
the desert?
The Mydid Fly is
active and mates
in the hottest part
of the summer.
The Antelope
Jackrabbit
is actually a
hare, not a rabbit
at all. Jackrabbits
rarely drink water.
They get all the
moisture they need
from the plants they eat.
Jackrabbits run in speedy
bursts up to 50 miles per hour.
The Jackrabbit’s foot-long ears help control
body temperature. During hot days, the long
ears stand straight up. Inside the ear’s thin
skin, a network of blood vessels gives off
heat, cooling the animal’s body.
On cold days, the ears lay back
close to the Jackrabbit’s body.
The Desert Cottontail
likes to munch on grass,
mesquite, and cactus.
Big-Eared Bats
hunt moths during the
night. Huge ears allow
them to fly and locate
food by sound, using
the echoes of their
ultrasonic squeaks.
Some bats can catch
up to 600 mosquito-sized
insects per hour.
K a n g a r o o R a t
11 http://chainreaction.asu.edu
The Roadrunner is the world’s fastest-running
flying bird. It prefers running to flying. About the
size of a skinny chicken, the speedy birds can take
12 steps in one second. Roadrunners have been
clocked zipping across the desert at speeds
up to 15 miles per hour.
The Collared Peccary is a piglike animal, but not actually a pig.
The name refers to the band of grayish-white fur around its neck. Heavy, bristly
hair covers a thin, muscular body. In Arizona, a collared peccary is known
as a Javelina. Javelinas have tough, leathery snouts, which allow the animals
to eat cactus and other spiny desert plants without injury to their mouths.
George Andrejko photos
The Bobcat snoozes on a warm
afternoon just like a housecat.
But don’t try to pet it!
The lone Coyote howling at the moon
is a symbol of the American West. In reality,
Coyotes are not solitary animals. They mate
for life and often hunt in packs, mostly
at night. Coyotes use at least 10 different
sounds to communicate, including barks,
yips, growls, and howls. Coyotes are
speedy runners. They cruise at 25 to
30 mph and can sprint at 40 mph for
short bursts, which is handy for catching
rodents, rabbits, and small deer.
The Ringtail cat is not really a cat.
Closely related to racoons, ringtails
are curious and active at night, some-times
stealing hikers’ food supplies.
Tiger Beetles are fast-moving
predators that catch and eat other
insects. They live in deserts and tropics
around the Earth. In India, people make
jewelry from the colorful wing cases.
Turkey Vultures
have a sinister reputa-tion
because they
eat stuff that would
make you hurl—
carcasses of dead
animals.
The Western Banded Gecko
feeds at night on spiders and insects.
C h a i n R e a c t i o n . 2 12
Th e Tarantul a Hawk is a big wasp.
The female uses a huge stinger to paralyze
tarantulas and other large spiders. Males
do not sting. The wasp lays a single egg
on the body of the paralyzed spider.
When the egg hatches, the maggot-like
larva burrows into the living spider and
begins to feed. The spider is helpless.
It actually may live for weeks or
months as the wasp larva devours
him from the inside out.
ASU biologist John Alcock
studies the big wasps. He marks
harmless males with paint. Alcock has
tracked a single wasp for up to 40 days in the field.
More than 35 different kinds of scorpions live in Arizona.
But only one species – the Bark Scorpion — has venom
potentially strong enough to kill a person. Don’t give
yourself nightmares. The last documented case in Arizona
of a person dying from a scorpion sting occurred in 1948.
A spider’s front jaws are called
chelicera. The chelicera
include the fangs.
The Giant Desert H a i ry Scorpion
is the largest scorpion living in the United States.
It can grow up to 6 inches long.
Desert scorpions never venture far from
the burrows they dig in loose, sandy soil.
“Chela” is the name for the scorpion’s
pincer-like appendages. Scorpions walk
with their chela extended.
Tarantulas and scorpions are arachnids.
Arachnids belong to the largest group of animals
now living on the Earth. Arthropoda is the scientific
name for this group, which scientists call a phylum.
Creatures in this group are called arthropods. The phylum
Arthropoda includes arachnids such as spiders, scorpions,
ticks, and mites. It also includes centipedes, millipedes,
crustaceans such as crabs, shrimp, and lobsters, and millions
of kinds of insects. Fossil evidence indicates that ancestors
to modern scorpions might have been swimming in
ancient oceans as long as 450 million years ago.
Paula Jansen photos
John Alcock photo
13 http://chainreaction.asu.edu
&stingers
fangs Tarantulas and scorpions are cousins. They may look like monsters from outer space,
but they actually are very shy creatures. They want nothing to do with humans. There are no
tarantulas in Arizona or the United States that are considered dangerous to humans. You are in
more danger from fainting and hitting your head than you are from the bite of a desert tarantula.
Mexic an Redknee Tarantul a
Tarantulas catch insects and tear them
into pieces. The pieces are rolled into
a large “food ball.” The spider then
gushes digestive fluids onto the ball
and slurps in the gooey bug stew.
Hard pieces are left behind.
In the Sonoran Desert, tarantulas spend
most of their lives living inside small
burrows that they dig in the desert soil.
They leave the burrow at night to hunt
for crickets, grasshoppers, beetles,
cockroaches, and other small creatures.
Better to be a girl? Most male tarantulas
only live between six and 18 months.
Female tarantulas can live for 20 or
30 years, depending on the species.
C h a i n R e a c t i o n . 2 14
RTraackintg tle
Camping g e a r a n d r e searc h eq u i p m e n t cram the back
of Emily Taylor’s truck. Beside her sits a plastic bucket secured with
a screw-top lid. Two female Western diamondback rattlesnakes
are snoozing inside.
Taylor is crossing reservation lands between Phoenix and Tucson to return
the snakes to the wild. She is headed toward the research site she and her
advisor, veterinarian Dale DeNardo, have staked out on land near the Tortalita
Mountains. Earlier that week in their ASU laboratory, the two scientists surgi-cally
implanted a radio transmitter under each animal’s ribs. Each transmitter
broadcasts a beeping signal at its own unique frequency. Using a receiver,
Taylor and DeNardo can locate the snakes in the field by following the signals.
This technology is called radio telemetry. The technology really helps
scientists who study reptiles. Just imagine trying to find the same snake twice.
In the past, researchers marked rattlesnakes by painting or injecting their
rattles with paint in coded patterns. That helped them to recognize a snake
if and when they were lucky enough to find it again.
Laboratory conditions can cause animals to behave differently than they
would in the wild. To study patterns in animal behavior, scientists must watch
the animals over time in their natural environments.Unfortunately, this makes
it very hard to keep track of them. Radio telemetry lets scientists find an animal
even when it moves to a new location.
The road into the research site soon turns into a heaving trail. Taylor shifts
into four-wheel drive. Her truck bucks its way to a wide space in the track.
She parks beneath heavy rust-colored buttes that rear up against a hazy sky.
It is just before dusk, the moment when shadows define the curves of desert
rock that look two-dimensional in midday sun.Armed with her radio receiver,
Taylor crunches through gravel to search for some of the more than 20 reptiles
she is following.
She and DeNardo are studying snake biology on several levels. First, they
want to document the basic ecology and habits of the western diamondback.
Scientists still have important questions to answer about the snake.Forexample,
no one knows much about its denning behavior.Why do animals that hunt and
sleep alone hibernate in groups?Why do researchers findmainly large,mature
males in those dens? Why do young and small males seem not to be included?
Emily Taylor’s
area of research
is called behavioral
neuroendocrinology.
She studies how
hormones trigger
an animal’s brain
to command certain
actions, such as
breeding.
by Kristine S. Wilcox
Herpetology:
The study of reptiles
and amphibians
In mammals, the fatter the animal, the
more leptin is found in the bloodstream.
In fact, leptin comes from fat cells.
The hormone tells the brain how much
fat the body has stored. When it detects
large amounts of leptin, the brain
signals the body to decrease feeding
and increase production of heat, which
uses energy. When leptin is low,
the brain tells the body to increase
feeding and decrease heat production
to conserve energy.
15 http://chainreaction.asu.edu/
ers Second, the ASU scientists want
to compare individual diamondbacks
within a particular area. Other
researchers compare individuals
of other rattlesnake species. Scientists will
eventually be able to put their knowledge together
and compare the various species from an evolutionary perspective.
Third, they want to learn how snakes allocate energy to reproduction.
Taylor’s main research interest lies in this area. She wants to know how
hormones in the female diamondback trigger breeding and the energy
use that fuels it. She says that the key is fat.
“In any female animal, fat is crucial to reproduction,” Taylor says.
“If an animal is undernourished due to drought or other stressful conditions,
she won’t attempt to breed that season. If she did, breeding would divert
fat from supporting her life systems to manufacturing yolk for her eggs.”
Taylor wants to know exactly what happens in a female snake’s brain
that tells her she has enough fat to breed. Taylor and DeNardo suspect that
a hormone called leptin is involved. Scientists know that leptin helps
to regulate eating and reproduction in mammals. They know that reptiles
produce leptin. But they don’t know what function the hormone plays
in the reptile body.
Researchers have learned that leptin allows female mammals tomenstruate
and ovulate. Taylor wants to know if it also signal a female mammal to breed.
If so, does this happen in rattlesnakes as well as mammals?
To answer these questions, Taylor and DeNardo spend four to five days
per week at the field site tracking their tagged reptiles.The scientists surrender
to the rhythms of the desert and live like lizards. They stalk prey in the cool
mornings and evenings. They snooze and swim at a nearby RV park during
the midday heat.
Typically, either Taylor or DeNardo arrives at the site in late afternoon.
He or she will track the animals until about 10 p.m. Then they sleep under
the stars and rise to track again with the sunrise. The goal is to follow the
animals through a season’s birthings, which occur in August. By November,
the rattlesnakes will retreat to dens for the winter.
The ASU scientists weigh the snake each time they recapture an animal.
By comparing a female’s pre- and post-birthing weights, they can figure out
how much fat and protein snakes invest in their babies. Two knots snarl
the research question. Taken alone, a female’s weight change does not show
“ how much energy she has put into reproduction. Exercise or diet rather than
pregnancy might have caused the change. Also, the researchers need to know
how much of the weight change is because of protein and how much is fat.
To find out, Taylor and DeNardo are using a technique commonly used
to measure body fat on humans. The method involves sending an electrical
signal through the body. The signal travels at different speeds through fat
and protein. After some number crunching, this information lets researchers
estimate the animal’s body fat percentage. Armed with this measurement,
the scientists will then factor in the animal’s movements (exercise) and the
food supply (her diet). They can then estimate how much body fat energy
the female has used to make babies.
Every three to four weeks, the researchers draw blood from the reptiles
to measure hormone levels. Taylor has one priority on this particular field visit.
She wants a blood sample from a female diamondback that she has been try-ing
to catch above ground for three weeks. With reptiles, the question
is always, is the animal up on the surface? Or is it down in a burrow? Radio
equipment may pinpoint an animal’s location. But if a rattlesnake is curled up
in a burrow, Taylor cannot just ring the bell and ask the snake to come out.
With her blonde ponytail swinging, a coiled serpent tattoo on her ankle,
Taylor strides along the soft-gravel washes that curve through the desert like
highways. Taylor holds the simple tools that protect her. In one hand is a pair
of plastic snake-handling tongs. In the other, a clear plastic tube, cloudy with
scratches, that is about as long as her forearm. A student intern lugs the plastic
bucket holding the snakes Taylor is returning.
Taylor always listens for the hissing rattle of a snake. She listens close in
washes where the scales of the diamondback blend into the gravel, and around
patches of prickly pear cactus, in which the vipers often seek burrows.
“The real danger out here is getting careless and stepping on a snake,”
she says. Suddenly, Taylor spots a snake. Stretching ahead of her in the wash
is a male diamondback, about three-and-a-half feet long. “Oh look at you,
bad boy,” Taylor says. “You are a beautiful boy.” She rushes toward the snake,
which tries to escape into the brush.
Rattlesnakes are slow. They cannot crawl more than about three miles per
hour. Taylor clamps her tongs around the snake’s body, holding it at full arm’s
length. The animal begins the defensive displays that it uses against predators.
Its muscled body thrashes. Its rattles clash furiously against one another.
Its pink cave of a mouth gapes and hisses. Foul smells seep from its cloaca.
With her right hand controlling the tongs, Taylor uses her left to bring the
tube toward the rattler’s head. Again and again the snake strikes the plastic
C h a i n R e a c t i o n . 2 16
Studying reptiles gives you a great evolutionary
Occupational
Hazard
“The term ‘usually’ should never
be applied to venomous reptiles,”
cautions rattlesnake researcher
Emily Taylor.
For example, snakes being coaxed
into a tube usually strike at the tube,
not the person holding it. But that
didn’t matter much when “Lucifer
the Jumping Snake” decided one day
to sink its fangs into Taylor’s hand
instead.
“He jerked his head out,” Taylor says,
“and sprang up to bite my hand.
Usually the snake won’t behave this
way. He’ll strike the tube, because it’s
the closest thing to his face.”
Nature is never entirely predictable.
Forgetting that in Lucifer’s case,
says Taylor, was her mistake.
Worldwide, every year, several hundred
thousand people are bitten by venomous
snakes. Of those, some 20,000 die.
Most deaths occur in Third World
countries with poor access to medical
treatment. Properly treated, snakebites
in developed countries cause death
in less than 1 percent of victims.
In the United States, most bites occur
when untrained people handle snakes
in the wild. Some victims die simply
because they refuse medical care.
Of nine snakebite deaths in Arizona in
recent years, three happened to victims
who refused treatment.
Almost all the old folk remedies for
snakebite are useless or dangerous,
according to experts. You should never
cut into a bite wound to suck out venom,
or apply a tourniquet unless a doctor
says to do so. >>
” with sharp snaps. The scientist is trying to lure the diamondback into the tube.
Finally it goes in, shooting about half the length of its body into the plastic
pipe. Now Taylor grips the tube and the tail end of the snake in one hand.
The tail hangs free, while the dangerous head is trapped in the tube.
“The snake could turn around in the tube, shoot back out and get your
hand,” Taylor explains. “Never take your eyes off a tubed snake.” She learned
this lesson the hard way (see sidebar).
Scientists don’t know why snakes enter the tube. “It may remind them
of heading into a burrow to escape a predator,” says Taylor. “Maybe it’s an
instinctive defensive move. They’ll fight going in, but sooner or later they all
go in.” Besides, she says, “They’re not super bright. The tube is in the forward
direction, and eventually they just go forward.”
Taylor pulls a syringe from her pack and bites the cap off the needle.
The intern takes the tube, and Taylor works the needle into the snake’s smooth
skin, seeking a vein near the rattles. She finds it and blood fills the syringe.
With another syringe she shoots acrylic paint into its rattles to identify it
with a three-color code.
Rattlesnakes are cold-blooded creatures. A snake feels cool to the touch.
Its body is very muscular. The underside feels slick as the hull of a fiberglass
boat. On top, you can click a thumbnail down the edges of the scales.
Taylor dumps the diamondback tail-first into a bag, then into the bucket
with the others. Later, she will weigh it, record its location, and return it
to the discovery site. This is the only new snake Taylor finds on this trip,
but she does find the female that has been eluding her. Taylor is thrilled to
draw the snake’s blood, saying how pleased her advisor will be that she got it.
Through the night and again the next morning at daybreak, Taylor doggedly
tracks each animal she must account for. She never loses her way, although she
crosses several square miles. The heat and exercise do not seem to tire her.
Her passion for her work keeps her energized.
Lots of peoplemight ask why Taylor is interested enough in snake hormones
to wrestle with rattlers. She points out that, for human beings, all biology
leads to self-understanding.
“Studying reptiles gives you a great evolutionary perspective,” she says.
“Remember, reptiles gave rise to mammals. Besides,” she adds, “some of the
biggest discoveries in science occur during basic research,kind of by accident.”
“I’m not saying that I expect to find the cure for AIDS by studying snake
hormones,” Taylor admits. But she does expect to add facts to the scientific
understanding of snakes.
17 http://chainreaction.asu.edu/
perspective,” Emily Taylor says.
“Remember, reptiles gave rise to mammals.
Poison control experts agree that the
best first aid for snakebite is to keep the
victim calm and warm to prevent shock,
and to seek medical help immediately.
In Taylor’s case, she received standard
treatment with antivenin—a serum that
neutralizes the poison.
She feared antivenin more than snake
venom. Antivenin is made from horse
serum. Horse serum causes intense
allergic reactions in 98 percent of all
patients. Symptoms can include rashes,
fever, and joint stiffness. Doctors treat
the reaction with steroids and antihista-mines.
Taylor did suffer a reaction after
her treatment with the antivenin.
But she responded quickly to treatment
and was handling snakes again within
a week.
“I have a renewed sense of care and
appreciation for these snakes, now,”
the ASU scientist says. She intends
to keep a “much larger buffer zone”
between herself and her snakes
in the future. Kristine S. Wilcox
Snake surgery Emily Taylor operates
on a captured rattler to implant a radio transmitter.
I n t h e S o n o r a n D e s e rt , some tigers hunt
during the day. Others hunt only at night. All desert tigers
use excellent eyesight to locate their prey, and then use
amazing speed to run it down.
The hunted creature has little chance. Once caught, the tiger crushes
it with huge, sickle-like jaws, and then tears it into pieces. The tiger pours
powerful digestive juices from its mouth onto the bits and pieces. Once
the pile of pieces is melted into a nice, gooey mush, the tiger rolls it all
into a large meatball. Then it is time to chow down.
Tigers in the Arizona desert? No way, you say. Believe it.
But these tigers are not giant cats. They are beetles. Their food
of choice includes ants and termites and small insects of all kinds.
David Pearson studies these fierce desert hunters. Pearson is an
ecologist and conservation biologist at Arizona State University. Tiger beetles,
he says, are fascinating, colorful predators. The insects are extremely popular
among amateur entomologists. Often brightly colored in greens, maroons,
or metallics, tiger beetles are the beauty queens of the insect world.
Pearson has circled the globe for his research,
studying beetles in South America, India, Africa,
Europe, Indonesia, and the United States.
Arizona is famous for its variety of tiger beetles.
The state is home to 36 different species, which live every-where
from the Chiricahua Mountains in southern Arizona
to the North Rim of the Grand Canyon. The beetles are
especially fond of the Sulphur Springs Valley in southeastern
Arizona, where 18 different species live. That is one of the
highest concentrations of species in all of North America.
Tiger beetles in Arizona grow from 10 to 25 millimeters
long. Most are brown or green with stripes. Most are active during the day.
Some are large and black and active only at night. The best time of year
to see tiger beetles depends on where you look.
The insects are active from February to April in Sedona and along
the Mogollon Rim near Payson. In July, they can be found in the White
Mountains. In southern Arizona, tiger beetles are active at the start of the
summer monsoons.
Pearson studies tiger beetles because they lend themselves easily to
conservation studies. These insects make good bioindicators. A bioindicator
is a species that serves as a representative sample of its ecosystem.
Bioindicators allow scientists to make predictions about the ecosystem
without studying every species in it. Tiger beetles are highly sensitive
C h a i n R e a c t i o n . 2 18
Teigrreirbsle
b y D i a n e B o u d r e au
O F T H E D E S E R T
Cicindela oregona maricopa—
Kim Wismann Photo
Cincindela lemniscata—Kim Wismann Photo
About 2,300 species of tiger beetles
(family Cicindelidae) exist worldwide.
They live everywhere there is land,
with the exception of Antarctica,
Tasmania, and some of the most
remote oceanic islands.
Tiger beetles primarily live in tropical
areas. The United States is home to
120 different species.
All the beetles shown here were found
in Arizona.
to changes in their environment, an important characteristic.
“In conservation biology we’re always short of money, time,
and personnel. We need to make policy decisions. Bioindicators
provide a quick way to find answers with a high degree of accuracy,”
explains Pearson.
“Bioindicators are kind of like the canaries in a coal mine,”
explains Pearson. “The canaries were very sensitive to methane gas—
much more so than human beings. These big burly miners would
carry down these little cages with canaries.
If the canary all of a sudden keeled over, people
ran quickly out of the mine, because they didn’t
have a lot of time, but at least they had some
kind of warning as an indicator of the danger.”
Tiger beetles vary in size.
The smallest lives in Borneo and
measures 6 millimeters, about the
length of a housefly. The largest lives
in southern Africa. It measures up to
45 millimeters, about the width
of a tea bag.
Tiger beetles come in many colors.
Some are plain black, but others are
stunningly decorated in metallic green,
brown, maroon, or purple, often with
stripes or spots. All tiger beetles have
long, thin mandibles shaped like
sickles, which help them capture prey.
Tiger beetle larvae use their mandibles
to dig tunnels in the ground, where
they wait for small insects to pass
close enough for capture. The larvae
stay in their tunnels from one to three
years before emerging as adult beetles.
An Australian tiger beetle takes the
prize as the fastest runner of all the
arthropods, a group that includes all
insects, crustaceans, and arachnids.
This beetle can move at 9 kilometers
per hour (5.6 miles per hour), or 170
body lengths per second. If it were the
size of a racehorse, the beetle would
be running about 120 miles per hour.
Consider this: a human traveling 170
body lengths per second would have
to run about 338 miles per hour, or 544
kilometers per hour! The tiger beetle
is a tough bug to catch, or to outrun.
19 http://chainreaction.asu.edu/
“You can’t just choose bioindicator
species because you like them,
because they’re soft and furry.”
Cincindela pulchra—Kim Wismann photo
Paula Jansen photo
Eleodes or darkling
beetle that has been dis-turbed
and is in the warning
position, with rear abdomen
6
Bugs It could be Halloween at Brimhall Junior High School in Mesa.
Kids are emptying bags. They count and compare their loot like hungry
trick-or-treaters. However, they are not finding candy bars and lollypops
in the bags. More like a bunch of ants and a handful of beetles.
Perhaps there are a couple of crickets
in the mix. Once in a while there
is a real prize—a giant centipede
or even a scorpion!
These treats are no trick.
The bags of bugs are actually part
of David Boomgaard’s science class.
They are also part of something bigger.
Brimhall is just one of several schools
taking part in the Central Arizona–
Phoenix Long–Term Ecological Research
project—CAP LTER for short. Scientists
from Arizona State University’s Center for Environmental
Studies and the CAP LTER project are studying how city life
in the desert affects our air, water, plants, and animals—including bugs.
The bug work is known officially as the Ground Arthropod Study.
Arthropods include insects, arachnids (such as spiders and scorpions),
crustaceans (lobsters, shrimp, and crabs), and myriapods (centipedes and
millipedes). Ground arthropods are creatures that
crawl on the ground. They do not f ly or swim.
Most people try to squash bugs. They shouldn’t.
Insects are actually a very important part of the
ecosystem, says Nancy McIntyre, the ASU scientist
in charge of the arthropod study. “There are more
different types of bugs than any other kind of living
organism on the planet,” she says. “They’re the most
diverse group of critters in the world.”
Arthropods also play important roles in
the environment. They are critical links in
the food chain, both as predators and prey.
They also aerate soil, pollinate crops,
and do a variety of other essential jobs.
There are lots of LTER sites all over
the United States. Scientists have
been doing long-term research on different habi-tats
for more than 20 years. But the Phoenix LTER
site is new. It is one of only two sites located in
cities. The other city site is Baltimore, Maryland.
C h a i n R e a c t i o n . 2 20
What is an Insect?
Insects have three major body sections:
Head, thorax, and abdomen
The head contains the one set of large
compound eyes, mouthparts, and one
pair of antennae
Six walking legs and one
or two pair of wings attach
at the thorax
Going Buggin’
by Diane Boudreau
darkling beetle
assumes the warning position.
This common desert beetle
protects itself by firing
a chemical that smells
and tastes bad. Have
you seen these beetles
in your neighborhood?
The hover fly looks and acts like a bee.
It’s a trick to make a harmless animal appear
uninviting to predators.
Conrad Storad photo
John Alcock photos
“Bugs in cities have been under-appreciated until very recently,”
McIntyre says. Now, CAP LTER researchers are finding that urban areas
are home to more than just roaches and ants. “It’s pretty amazing that a city
as large and as sprawling as Phoenix has such a diverse bunch of bugs.
So far, we’ve captured nearly 90 types of arthropods here,” says McIntyre.
CAP LTER scientists collect bugs from 24 sites. The sites are divided
into six different types of habitats. Phoenix-area schools that participate
in the bug study add their own special habitat: schoolyards.
“We wouldn’t normally have access to a whole bunch of schools,”
McIntyre says. “We wouldn’t have the people power, we wouldn’t have
the time, and we wouldn’t have the money.” So teachers and students
contribute a lot to the project. Twenty schools are involved in the project
at this point, almost doubling the number of sites being studied.
CAP LTER’s Ecology Explorers program works with local schools to teach
kids about ecology and get them involved in the experiments. Monica Elser
is an education liaison for Ecology Explorers. She says that Arizona students
basically do the same research as the CAP LTER scientists.
The first step is to set traps to catch the bugs. Students bury plastic
cups so that the tops are level with the ground. Bugs fall into the cups,
but they can’t climb out because the sides are too slippery.
The Grey Hairstreak
is a highly territorial butterfly.
The males defend perching sites on hilltops.
The Buprestid Beetle
is a wood-boring insect.
Some types specialize
in feeding on the pungent creosote bush.
Great Purple Hairstreak adults
sip nectar from mesquite and mint flowers.
The caterpillars feed only on the
leaves of mistletoe.
21 http://chainreaction.asu.edu/
CAP LTER scientists collect bugs from 24 sites.
The sites are divided into six different types of habitats:
+homes with lawns
. homes with desert landscaping
P industrial areas
R farmland
e desert parks within the city (like Papago Park)
b desert parks on the edge of the city (like Estrella Mountain Park).
Phoenix-area schools that participate in the bug study
add another category to the mix:
c schoolyards
Black Widow
venom, drop for drop,
is 15 times more powerful
than that of a rattlesnake.
But a rattlesnake is
much more dangerous
because it produces
much more venom.
Marty Cordano photo
John Alcock photos
8
What is an Arachnid?
Arachnids have only
two major body sections:
Cephalothorax and abdomen.
Head and thorax are fused to form
the Cephalothorax; a thin waist
connects the two body parts.
Eight walking legs
Many eyes, as many as 6 or 8
No antennae
No wings
After collecting the bugs, the kids immediately put them into labeled
Ziploc bags. Then they freeze the bags, bugs and all.
Elser says the freezing is very important. It is difficult to study bugs
closely enough to identify them when they are moving. Freezing is also
an important safety measure, because students occasionally catch scorpions
and other venomous arthropods.
Students identify the creatures using a key that CAP LTER provides.
They catalogue the bugs by order, such as Hemiptera (true bugs) or Coleoptera
(beetles). The students count how many of each type they find, and then
send the data to the CAP LTER Web site on the Internet.
“The kids become experts at identifying the insects.
They don’t need the keys after a while,” Boomgaard says.
“I couldn’t even identify them before I joined
the program, and I’m a biology teacher!
“We mostly find beetles and ants. Every
once in a while we get some surprises,” he adds.
“We’ve caught some bees, which are a surprise
because normally they just f ly away. We’ve
caught crickets and cockroaches. We even
get the odd gecko or two in the cups.”
Elser says that most students find lots of
beetles, grasshoppers, crickets, roaches, true
bugs, and ants. Once in a while, students will
find a scorpion or giant desert centipede as well.
McIntyre hopes the program will teach
kids not to just kill bugs automatically. “A lot of
people are really afraid of arthropods,” she says.
“They think they’re going to bite or sting, but
most of them don’t. I know from personal expe-rience
that when people are afraid of things they
tend to kill them. A great example is dragonflies.
People are scared to death of dragonflies.
But dragonflies are completely harmless.”
Not only are most bugs harmless, many of them are pretty, too. “There
are a lot of beautiful patterns that you can only see up close,” Elser says.
What do Boomgaard’s Mesa junior high students think of the project?
“I remember a kid saying last year, ‘This is really cool. We don’t just
learn about science, we go out and actually do it,’” Boomgaard says.
The CAP LTER scientists are just as happy about the project.
“All the students are helping us out,” says McIntyre. “They cover
20 sites that we wouldn’t otherwise be able to study.”
Bugged by Bugs
It flie s. It crawls.
It is small and funky-looking.
It’s a bug,
right? Well, not
exactly.
Most people use
the word “bug”
to refer to all
insects. But tech-nically,
not every
insect is a bug.
True bugs, as they
are called, do not
include such buglike
creatures as ants, bee-tles,
or flies.
True bugs look
a lot like beetles, because they
have hard shells and wings. The dif-ference
is in their mouths.
Beetles have mouths designed for
chewing. True bugs have long snouts
designed for sucking sap from plants.
Flies, mosquitoes, yellow jackets,
midges, and gnats often make it a habit
to bug people. The next time they start
bugging you, remember that they are
not true bugs at all. They are insects.
Tell them to “Bug Off.”
To learn more about the CAP LTER
Ecology Explorers program, contact
Monica Elser at 480.965.6046 or
Susan Williams at 480.965.1961.
E-mail to ecology.explorers@asu.edu.
Or,visit the Ecology Explorers Web site—
http://caplter.asu.edu/explorers/
C h a i n R e a c t i o n . 2 22
{A Pa i r o f D u n g B e e t l e s just making a living. They roll a ball of cow dung
to a burrow where they lay eggs. The dung will feed the grubs when they hatch.
Arthropods
aerate soil,
pollinate crops,
and do a
variety of other
essential jobs.
The Long-Horned Wood Boring Beetle male defends
saguaro fruits in order to mate with females attracted to the food.
John Alcock photos
B i r d s , b i r d s , b i r d s .
Phoenix is a city filled with birds.
Birds of many kinds. Birds of many colors.
Some of these birds are native to the Sonoran Desert. Some are
birds that have moved here to stay. And some are birds that are just
passing through on their way to nesting grounds in other locations.
How many different kinds of birds live in Phoenix? No one is sure,
for now. But lots of people are watching and counting birds to find
the answer. If you see a stranger lurking around your neighborhood
with binoculars at dawn, don’t be alarmed. Chances are, you’ve come
across a volunteer birdwatcher taking part in an important study.
The study is part of the Central Arizona-Phoenix Long-Term
Ecological Research (CAP LTER) project at Arizona State University.
Scientists in charge of the project want to find out what kind
of impact all the new building and development is having on bird
communities throughout the Phoenix metropolitan area.
About 90 local volunteers are helping to collect this information.
Armed with binoculars and notebooks, they walk through Phoenix area
neighborhoods at sunrise. They make note of all the birds they see or hear.
Joan Powers is a volunteer. “Initially I got stopped a lot,” she says.
“People get wary when you’re walking around with a clipboard and
binoculars at odd hours of the day.” Today, people living in the neighbor-hoods
patrolled by Powers recognize her. “I’ve been doing this for more
than a year,” she says. “Lots of people know me now. They ask, ‘What new
birds have you seen today?’”
“This study provides a unique opportunity to involve the public,”
says Mark Hostetler, a postdoctoral fellow at ASU who designed the
bird survey project. “The majority of the population lives in urban areas.
Urban areas are expanding dramatically. But we don’t really understand
them. Ecologists don’t really focus on urban areas. We’d rather hang
around in forests,” Hostetler laughs.
The main goal of the bird study is to establish
a pattern. Is that pattern consistent year after year?
What are the mechanisms causing the patterns?
For example, does housing density or road traffic
affect bird populations in Phoenix?
Volunteers typically study a one-kilometer area divided
into 10 segments. They make a note of all the birds they
can see or hear. Some professional birders also participate.
These bird-watching pros study four key habitats: golf
courses, new residential neighborhoods, older residential
neighborhoods, and desert remnants like Papago Park.
Cardinals love the Sonoran Desert.
Just like human "snowbirds," they
flourish in places where winters are
mild.
The Black-Headed Grosbeak
has a conical beak adapted for
crushing seeds.
Phoenix is one of two urban areas
selected for long-term ecological study.
The other city being studied is
Baltimore, Maryland. “Long-term” is an
important part of the study, according
to ASU scientists. Most studies like the
bird survey only last for a year or two.
CAP-LTER research, however, is funded
for at least six years.
Birds Phoenix: A City for the
By Diane Boudreau
23 http://chainreaction.asu.edu/
Robert Ohmart photo
Charles Kazilek photo
Wwhea t know
so far:
Most days, Powers sees about 15 of the
same basic kinds of birds. But spring migra-tion
often brings in some odder species.
ASU scientists hope to learn more about
migrating birds that stop to rest in Phoenix.
“Nothing is known about stopover ecology,”
Hostetler says. “We’ve seen lots of migrating birds
coming through. There are more birds in Phoenix than outside
the city. But the composition is different.”
The bird survey provides information that is useful to ecologists.
ASU researchers say early findings of the study are that building and
landscape design play a bigger role in attracting birds than zoning.
In other words, the style of buildings and the type of vegetation around
them matters more than whether they are houses, stores, or factories.
This information could help designers plan more bird-friendly neigh-borhoods.
Developers can use it to create communities that are more
attractive to birds. The researchers are even trying to connect with
realtors, encouraging them to use birds as a selling point.
ASU scientists think that involving the public is one of the best parts
of this project. Many of the volunteers are retired people. Children and
teachers from many local schools also help to collect information about
birds. Teachers are trained to lead their students in conducting point counts.
They stand in one place and count the birds in a 20-meter radius over
a certain time period. Then they send the data in to the kids’ section
of the CAP LTER Web site.
One goal of the project is to help connect urban
kids to their environment. When he gives talks
at schools, Hostetler often asks kids, “Where do
chickens come from?” Many of them will name
the local supermarket! “Urban life is great—
we have all these conveniences—but it’s
disconnected from nature. Understanding how
humans affect the environment can help us
minimize our impact.” Hostetler explains.
C h a i n R e a c t i o n . 2 24
Prairie Falcon
Cactus Wren
Redtail Hawk
Daryl Abbott /Southwest Wildlife
Rehabilitation Center
George Andrejko photos
George Andrejko photos
CAP LTER Bird Survey findings
Building and landscape design
play a bigger role in attracting birds
than zoning.
Escaped pet birds are thriving and
breeding throughout the Phoenix area.
“In my study area we have a population
of peach-faced lovebirds that has been
surviving and enduring. They obviously
escaped out of someone’s house,” says
Joan Powers. Peach-faced lovebirds are
native to hot, dry African habitats.
Arizona has all the comforts of home
for them. Unfortunately, these sweet
green birds with the rosy faces may pose
a threat to native Arizona birds. They are
potential competitors against wood-peckers
and other birds. The lovebirds
can take over giant saguaro cactuses.
Powers says that lovebirds aren’t the
only escapees she sees. Parakeets and
parrots have also shown up on her list.
Phoenix Bird Survey Study data
is available to everyone at
http://caplter.asu.edu/po12.
Visitors can learn exactly what species
live where. To learn more about
other CAPLTER projects visit
http://caplter.asu.edu/explorers/
25 http://chainreaction.asu.edu/
The Gil a Woodpecker is an
important part of the Sonoran Desert
animal community. Every spring,
male and female woodpeckers work
together to peck a deep hole in the
thick stem of giant saguaro cactus
or in the trunk of a cottonwood tree.
Elf Owls and other birds make their
nests in old woodpecker holes.
Lizards and spiders and insects of
many kinds also live in the old holes.
George Andrejko photo
Tim Trumble photo
Robert Ohmart photos
Anna’s Hummingbirds
live in the fast lane. To get the
energy they need for hovering,
hummingbirds must eat half
their body weight in sugar
each day. Some species beat
their wings as fast as 80 times
per second. Proportionally,
a hummingbird’s heart is
the largest of any animal.
Gambel’s Quail
is quite easy to recognize
by the black tear-shaped plume
on top of its chestnut brown head.
Gambel’s Quail has a loud, cackling
call that repeats three syllables.
The second syllable has the
highest pitch. The quail’s
ringing call is a true sound
of the Sonoran Desert.
Pyrrhuloxia gets its name
from Latin and Greek words meaning
"bullfinch with a crooked bill."
Northern Oriole has a clear, flute-like call.
It whistles single or double notes in short bursts.
Numbers
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N U M B E R S
A N D
B I O L O G Y
More than 1 quintillion insects–
1,000,000,000,000,000,000–
live on Earth on any given day. By 2000,
there were a little more than 6 billion
humans—6,000,000,000.
Scientists have discovered and
described more than 900,000 different
kinds of insects—more than 75 percent
of all the known animals on Earth.
There may be as many as 30 million
more kinds of insects yet to be
discovered.
There are more than 30,000 known
species of spiders. About 2,500 kinds
of spiders live in North America.
The not-so-magic tool they use is called statistics.
Statistics is a type of mathematics used to organize and understand data.
Data are figures and symbols. Data include all the raw, unprocessed facts
that scientists gather during their experiments and measurements.
Scientists use statistics to give meaning to all these raw facts and
numbers. Statistics help scientists describe how things are right now.
They also help to make predictions about how things will be in the future.
For example, ASU professor Harvey Pough wanted to know if he could
help desert tortoises grow up faster by feeding them high-protein diets
(See story, page 22). He started with 24 tortoises. Half were fed a protein diet
and half a salad diet. Then he weighed all of the tortoises. The result was
12 different numbers for each tortoise group.
Pough used statistics to find out the average weight of tortoises in each
group. He found that tortoises on the protein diet weighed an average
of 800 grams. But tortoises in the salad group weighed an average of only
360 grams. Those results gave Pough an answer—the protein tortoises were
definitely growing faster.
Statistics are especially useful when you need to learn about huge groups
of subjects. For instance, ASU scientists working on the Central Arizona-
Phoenix Long-Term Ecological Research project want to know
how urban development and land use affects the number of bugs in Phoenix
(See story, page 20). But they can’t possibly count every single bug in all
of Phoenix—it would take them forever! Instead, the scientists carefully
chose a few sections of Phoenix to study. They count all the bugs
in those small areas. The areas they chose are called a representative
sample because, added together, all the areas represent the whole city.
The scientists make lots and lots and lots of measurements. Then they
use statistics to find out what their sample says about the whole population
of bugs in Phoenix. For example, if they find 47 beetles in their park area
sample, they can estimate how many beetles there are in all Phoenix parks.
John Wallace is a 9th grade teacher at Mountain Ridge High School. His
students used statistics to find out whether urban development has affected
the number of bruchid beetles and palo verde trees in their school district.
Bruchid beetles lay their eggs on the seedpods of palo verde trees.
The eggs hatch into larvae, which burrow into the pods and eat the seeds.
The larvae grow inside the pods and come out as adult beetles.
Wallace’s students collected seedpods from trees in their school district
and from trees in a rural area outside Phoenix. They studied the rural area
to get an idea of how things were before their school district was devel-oped.
The students counted the number of pods found in each area, and
the number of beetle holes in each pod. The beetle holes told them how
many beetles were born.
C h a i n R e a c t i o n . 2 26
Tell The
Story…
Sometimes.
Scientists try to
answer questions about
the world around us.
That is their job.
To do this, they design
experiments and make
lots of measurements.
The result of all this work
is usually a long list of
numbers. So how exactly
do scientists turn all
those numbers into
meaningful answers?
by Di a n e B oudr e au
27 http://chainreaction.asu.edu/
T r a p 1 T r a p 2 T r a p 3 T r a p 4 T o t a l
Thought Question
Scientists are not the only people
who use statistics and graphs. In fact,
statistics are used in almost every part
of life. Your teacher uses statistics
to come up with your average grade.
Political polls use statistics to predict
who will get elected president.
Where else can
you see statistics
in use?
1 6 10 2 1 1 20 2 4 8 7 0 3 0 11 0 9 15 48 4
S p i d e r s
B e e t l e s
A n t s
C r i c k e t s
The findings for inside and outside the city were different. Using statistics,
the students learned that this difference was significant—it was a real effect
of urban development, not just random chance.
But were there more or less pods and holes inside the city? The answer
was surprising.
There were more seeds inside the city than outside, probably because
city trees are well irrigated. But what about the beetles?
“If all you had was the seed data you might think there would be more
beetles, because the beetles eat the seeds,” says Wallace. “In fact, we found
more holes per pod in the wild sample.”
After researchers analyze their data with statistics, they need to share
it with other people. One of the easiest ways to do this is by creating
a graph. Graphs take statistical information and make it into a picture.
People looking at the graph can understand the data at a glimpse.
Let’s look at an example. Suppose a scientist was catching bugs in four
different traps. On one particular day he counted the following bugs:
Trap 1: 1 spider, 6 beetles, 10 ants, 2 crickets
Trap 2: 1 spider, 1 beetle, 20 ants, 2 crickets
Trap 3: 4 spiders, 8 beetles, 7 ants, 0 crickets
Trap 4: 3 spiders, 0 beetles, 11 ants, 0 crickets
Now look at the graph below.
Which way of showing the data
gives you a better understanding
of what the scientist found? Why?
Woodley is a biology doctoral student
at Arizona State University. Her scientific
instincts overrule her instincts as a hiker.
That’s why she sits quietly in the forest.Woodley
accepts the risks in order to study the aggression of
female mountain spiny lizards.
For the past three years, Woodley has studied the behavior of these five-inch-
long reptiles. She collects blood samples to study their hormones and
observes the animals to see how they behave.
Lots of mountain spiny lizards live along the wood-lined creeks of Arizona
mountains like Mt. Graham. The lizards are good candidates for scientific
studies because they are easy to watch and easy to catch. Both male and female
mountain spiny lizards are intensely territorial. They do furious pushups that
send the message, “Here I am! Don’t come into my territory!”
At least that is Woodley’s interpretation of lizard body language.
Woodley studies how hormones inf luence female aggression
in mountain spinys. Female mountain spinys are more aggressive than
females of other lizard species. They will defend their territories by
displays of pushups or by extending their dewlaps (throat f laps).
They also charge and bite intruders. In male animals, the hormone
testosterone leads to aggression. But scientists don’t know why many
females also behave aggressively, Woodley says.
During her last field study, Woodley worked in a forested area about
6,000 feet up the side of Mt. Graham. The mountain is located in the Coronado
National Forest about 60 miles northeast of Tucson. Mt. Graham is black bear
country, and Woodley has seen her share. The hiker in Woodley knew that
she was supposed to make noise to scare them away. Scientist Woodley had
to remain silent.
Thought Question:
In what other groups
of animals do the females
compete for food and territory?
Hormones are chemical messengers
produced by endocrine glands.
They travel through the bloodstream
to reach different parts of the body.
When they reach their destinations,
hormones give instructions for
controlling growth, metabolism,
sexual reproduction,
and other body processes.
Learn more about hormones
and lizard behavior—
Visit the website at
http://askabiologist.asu.edu
/research/tlizards
B I O L O G Y
A N D
C H E M I S T R Y
C h a i n R e a c t i o n . 2 28
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A good hiker visiting
Arizona’s 10,717-foot
Mt. Graham would make
plenty of noise to frighten
bears away. Backcountry
visitors would steer clear
of javelinas and rattlesnakes
to avoid provoking them.
And no one would risk
attracting lightning by
carrying a metal fishing pole
along a mountain trail
during monsoon season.
No one except Sarah Woodley,
that is.
Following the Fighting Females
by Dennis Durband
She was more wary of the javelinas—because of their sharp canine
teeth—and the “jumpy” cattle that graze through the forest.
Snakes often ate her lizard
subjects while she was
studying them.
Monsoon thunderstorms
filled the sky late in the afternoons.
Woodley got soaked many times. Despite the
attractions and distractions, she made her obser-vations
and collected 60 female spiny lizards over
a seven-week period.
In a laboratory at ASU, Woodley performed
surgery on each of her captured reptiles.
She removed some of the lizards’
ovaries—glands that produce
eggs and female hormones.
She gave others a testos-terone
implant.
A second group of lizards served as controls.
The control group underwent fake surgery. Woodley
didn’t remove or implant anything on these lizards.
None of the lizard surgeries harmed the animals.
They were put to sleep so they didn’t feel any pain. Surgery only lasted about
15 minutes, and all of the lizards survived. Each patient went home the day
after surgery. Each was marked with a harmless paint stripe for identification.
Woodley says the lizards acted skittish for several days. So she waited three
weeks before making new behavioral observations. During those three weeks,
she visited the site every other day to help the lizards get used to her presence.
Woodley watched to see how the surgically altered females reacted to
intruders. She used a fishing pole and dental f loss to place intruders on rocks
in the territories of other females.
Females without ovaries showed a decrease in aggression. Since ovaries are
the main source of the hormone estradiol, Woodley believes that estradiol
plays some role in aggression. However, the female lizards with testosterone
implants rated high in displays but low in charging intruders. The testosterone
wore off over time. Woodley thinks the hormone may have caused females
to exhibit male-like courtship displays.
Fake surgery did not seem to change the lizards’ behavior. More than
70 percent of those females charged and bit intruders as usual.
Woodley’s research is important because most scientists have assumed that
aggressive competition is a characteristic of males. They have ignored the large
number of situations where females aggressively compete.
What is a
Control Group?
Control groups are an important part
of many scientific experiments.
Researchers use control groups to find
out if a treatment really has an effect.
Sometimes, study subjects act differ-ently
after treatment just because they
know they got treated.
Suppose that you go to your doctor
and tell her that you can’t sleep at night.
She gives you a pill to help. You go
home, take the pill, and fall right to
sleep. The pill did the trick, right?
Maybe. Or, maybe you believed the
pill would work, so you quit worrying
about falling asleep. You got so relaxed
you had no trouble sleeping. It was
your state of mind, not the pill itself,
which helped you.
The way to find out what really worked
is to conduct an experiment using a
control group. In this type of experiment,
about half of the subjects would receive
the real sleeping pill. The rest would
receive a fake pill, usually made of
sugar. The fake pill is called a placebo.
None of the subjects would know which
pill they got.
After the experiment, the researcher
would compare the results. If the
people taking the real pill fell asleep,
but the control group didn’t, then we
woould know the pill works. If both
groups fell asleep, then we would know
that the act of taking the pill, not the
pill itself, was what worked. This is
known as the “placebo effect.”
Even animal researchers often need
to use control groups. For instance,
Sarah Woodley wanted to know if
removing a lizard’s ovaries would change
the lizard’s behavior. She needed to be
sure that the loss of ovaries, not the
experience of capture and surgery, was
what caused any change. Woodley used
a control group of lizards. The “control”
lizards went through surgery, but kept
their ovaries.
Can you think of some reasons why
a lizard might be less aggressive after
surgery, even if the surgery is not quite
the real thing? —Diane Boudreau
29 ht tp://chainreact ion.asu.edu/
Thermoregulation:
The management of body heat is called thermoregulation.
Without proper thermoregulation, animals cannot survive. To understand
thermoregulation, it is important to know a little bit more about heat.
In the 1700s, scientists thought of heat as a mysterious f luid, which they
called "caloric." They thought that heat f lowed froma hot into a cold substance
in the same way water flows from a full into an empty cup. For more than
100 years, the caloric idea helped to explain observations about heat.
Ideas changed in the mid-1800s. New observations about heat could
not be explained in terms of the caloric idea. Today, heat is just one part
of the modern theory of thermodynamics. The theory says that heat is
a form of energy, not a mysterious f luid. But we still say that heat "f lows."
Scientists know that heat inf luences temperature. When a substance
contains lots of heat, it is hot. When it contains little heat, it is cold.
The amount of heat in a substance is called its heat content. When a hot
substance is put in contact with a cold substance, both substances eventually
become warm. They reach a state called “thermal equilibrium.” Heat from
the hot substance f lows into the cold substance until it is balanced
between the two. As a result, both substances reach the same temperature.
That temperature stays the same over time.
If left alone, heat always f lows from hot to cold. This is the direction
of spontaneous f low. “Spontaneous” means that the f low happens all
by itself. No usable energy is consumed.
Substances or materials often come in contact with one another.
During that contact, heat can f low from one substance to the other.
This process is called conduction.
Any substance, including the skin, feathers, or fur of desert animals,
is always in contact with its surroundings. That substance is always exchanging
heat with those surroundings. If heat is added faster than it is lost, the heat
content and temperature of that substance will increase. If heat is lost faster
C h a i n R e a c t i o n . 2 30
The Wright
Stuff
BY DAVID WRIGHT
Hot
Enough
For You?
The caloric idea lasted
as an explanation for heat
because it described many
commonly observed effects
of heat.We now know
that heat is the energy
of moving molecules.
This explains the most
careful observations we
can make of heat effects.
The molecules in liquids
and gases bounce off each
other like bumper cars.
The molecules can’t move
around in solids. They
vibrate in place, as if held
together by tiny springs.
Animals of all kinds
live in hot, dry South-western
deserts.
These creatures have
adapted to survive
sizzling summer days
and frosty winter nights.
To stay cool, a desert
animal must avoid
and shed heat. To stay
warm, the creature
must gather and store
heat in some way.
than it is added, heat content and temperature will decrease. If heat is added
and lost at equal rates, the heat content and temperature will not change.
Every substance has a different ability to hold heat. This ability is called
the heat capacity of the substance. Different substances have different heat
capacities. As a result, they can have different heat contents, even though
they may exist at the same temperature.
Imagine that heat really is f luid and that a substance is a cup. The diameter
of the cup represents its heat capacity. The amount of f luid in the cup is the
heat content. The height of the f luid in the cup represents the temperature.
The desert is hot because the soil absorbs heat from intense sunlight.
This is called radiant heating. Sunlight is a form of radiation that contains
many different kinds of light, including infrared light. Infrared light carries
heat and is not visible to the human eye.
Perspiration is efficient for cooling,
but only if the air is dry. If the air is
humid, the evaporation process is slow.
Heat is not removed quickly. Unfortu-nately,
perspiration requires a large
amount of water, which usually
is scarce in the desert.
Many desert animals do not have
sweat glands. Birds and rodents, like
dogs, must pant to cool themselves.
When they inhale dry air, water found
on the linings of the lungs evaporates.
The evaporating water absorbs heat
from the lungs. Heat is exhaled along
with the water vapor. But if these
creatures become dehydrated,
they will overheat.
This is what sweat looks like on the surface
of your skin—enlarged thousands of times by
electron microscope. The image was made from
a latex rubber mold of a fingerprint. Living things
cannot be viewed in an electron microscope because
the energy of the electron beam used to illuminate
the subject would fry it!
31 http://chainreaction.asu.edu/
H e a t c a p a c i t y
L o w H i g h
Heat flow from warmer to cooler
T e m p e r a t u r e
The same heat content can result in different temperatures,
depending on the heat capacity of the substance.
Examples of average
body temperatures
Birds: 100-112° F
Rabbits, sheep and cats: 102.2° F
Horses: 100.4° F
Whales: 95.9°F
Humans: 98-99° F
(in America and France, “normal”
is set at 98.6°. In Great Britain,
98.4° is considered the normal point).
Some mammals hibernate
in the winter and drop
their body temperatures
during this time. The most
extreme example is the
Arctic ground squirrel,
which can drop its body
temperature to 28.4° F
while it hibernates.
C h a i n R e a c t i o n . 2 32
Conduction from the desert soil causes the air to get hot. The air expands.
As it becomes less dense and more buoyant, the hot air rises. To replace
the rising hot air, cooler air from above sinks to the desert f loor. That air
then absorbs heat and the cycle continues. When heat moves because hot air
rises and cool air sinks, the process is called convection.
Desert animals have adapted ways to stay cool during the hot desert day.
They stay in shade or find a cool place underground to avoid radiant heating
and conduction fromthe soil.Most desert animals are nocturnal,whichmeans
they are active only at night. This is thermoregulation through behavior.
Thermoregulation also depends on the way in which heat inter-acts
with matter. Substances can exist in solid, liquid, or gas form.
The form, or phase, of a specific substance is determined
by its heat content. Think about water. If ice absorbs heat,
it will melt to form liquid. If the liquid absorbs heat, it will
evaporate to form steam or vapor. However, if that water
vapor loses heat, it will condense to form liquid. If the liquid
loses heat, it will freeze into ice.
The change between phases is called a transition. For animals,
evaporation is an important process for cooling—melting, freezing, and
condensing are not practical methods for thermoregulation.
For example, if an animal has enough water in its body, it can use
evaporation to stay cool by perspiration (sweating) and respiration (breathing).
Animals with sweat glands perspire to cool large areas of skin. Water is
secreted through pores in the skin. When it evaporates, the water vapor
carries away heat from the skin.
Lizards, snakes, and other cold-blooded animals cannot generate body
heat from the energy in their food. To stay warm, they absorb the heat they
need from the surrounding environment. They absorb heat directly from
sunlight. They also use conduction to absorb heat from the hot desert soil.
They retain that heat by insulation.
Coyotes, javelinas, rodents, birds, and other warm-blooded desert animals
also absorb external heat. But they also use chemical energy from food
to generate large amounts of internal body heat.
As long as food is plentiful, warm-blooded animals have a distinct
advantage for thermoregulation. Warm-blooded animals can stay warm
even when it is cold outside for long periods of time. On the other hand,
cold-blooded animals don’t need as much food to survive extreme
temperatures because these creatures don’t use the energy from their
food for thermoregulation.
i n s u l at o r s
Temperature is
a measure of heat.
There are several
different temperature scales.
The Fahrenheit scale is the oldest
system for measuring temperature,
still common in the United States.
ItwasinventedbyGermanphysicist
named Daniel Gabriel Fahrenheit
in 1724. He set the freezing point
of water at 32 degrees, and the
boiling point at 212 degrees.
Anders Celsius invented the Celsius
scale in 1743. He set the freezing
point of water at 0 degrees and
the boiling point at 100 degrees.
This system is now used in most
countries and among scientists
everywhere. It is also called the
Centigrade scale.
The Kelvin scale measures the ultimate extremes
of temperature. It was invented in 1848 by Lord
William Thomson Kelvin. In the Kelvin system,
zero degrees — or “absolute zero” — is the
temperature at which there is no molecular
motion and therefore, no heat at all. There is
no temperature colder than absolute zero.
Absolute zero is equal to -273 degrees Celsius
or -460 degrees Fahrenheit.
Heat flows quickly through some
substances. These are called thermal
conductors. Heat flows slowly through
substances that are thermal insulators.
The flow of heat into or out of a substance
depends on conduction. The storage of heat
depends on insulation. Thermoregulation
depends on both conduction and insulation.
Substances that are good thermal conductors:
metal or water.
Substances that are good thermal insulators:
wood, bone or rock.
What characteristics of these materials
affect heat flow?
Desert birds, like this turkey vulture, often soar
effortlessly for hours by riding on thermals,
the updrafts of rising air created by convection.
By gliding on thermals, the birds conserve
precious energy as they hunt for food.
c o n d u c t o r s